Hard Disk not recognized by System

The system cannot be started from the hard disk, nor can the system be started from disk A into disk C, nor can the automatic monitoring function in CMOS be used.
Hard Disk found. Most of these failures occur on the connection cable or IDE port. The failure of the hard disk itself is unlikely. You can re-plug the hard disk cable or change the IDE port and cable to conduct replacement tests, you will soon find the fault. If the new hard disk is not accepted, a common cause is the master-slave jumper on the hard disk. If an IDE hard disk is connected to two hard disk devices online, the master-slave relationship should be clearly defined.

Fault Caused by CMOS

Whether the hard disk type in CMOS is correct directly affects the normal use of the hard disk. Currently, all machines support the "Ide Auto Detect" function to automatically detect the hard disk type. When the hard disk type is wrong, sometimes the system cannot be started, sometimes the system can be started, but a read/write error occurs. For example, if the hard disk type in CMOS is smaller than the actual hard disk capacity, the sectors behind the hard disk cannot be read or written. If the disk type is multi-partition, individual partitions will be lost. There is another important cause of failure. Because the current ide supports the Logic Parameter type, the hard disk can adopt "normal, LBA, large" and so on. If data is installed in normal mode, changing to another mode in CMOS will cause a read/write error on the hard disk. Because the ing relationship has changed, the original hard disk location cannot be read.

Startup Fault Caused by the Main Boot Program

The primary boot program is located in the primary Boot Sector of the hard disk. It is mainly used to check the correctness of the hard disk partition, determine the active partition, and hand over the boot right to the DoS or other operating systems of the active partition. If the program is damaged, it cannot be booted from the hard disk, but the hard disk can be read and written after being started from the soft drive or optical drive. The solution to this fault is relatively simple. It is most convenient to use the fdisk of the higher DOS version. When the fdisk with parameters/MBR is running, the primary boot program of the hard disk will be directly replaced (overwritten. In fact, the Main Boot Sector of the hard disk is created by this program. fdisk. EXE contains the complete Main Boot Program of the hard disk. Although the DOS version is constantly updated, the Main Boot Program of the hard disk has not changed, from DOS 3. for DoS from X to ipvs 95, you only need to find a DOS boot disk to start the system and run this program to fix it.

Startup Fault Caused by Partition Table Error

Partition Table errors are serious hard disk errors. Different levels of errors may cause different losses. If there is no active partition flag, the computer cannot start. However, you can read and write the hard disk after the drive or the Drive boot system. You can use fdisk to reset the active partition for repair.

If a partition type is incorrect, the loss of a partition may occur. The fourth byte of the partition table is the partition type value. Normally, the basic DOS partition value larger than 32 MB is 06, and the extended DOS partition value is 05. Many people use this type of value to encrypt a single partition and restore the original correct type value to restore the partition to normal.

The partition table contains other data used to record the start or end address of the partition. Damage to the data will cause confusion or loss of the partition. The available method is to re-write the data in the backup partition table, you can also obtain partition table data from other hard disks of the same type and with the same partition status.

The recovery tool can use tools such as nu for easy operation. Of course, you can also use DEBUG for operations, but the operations are cumbersome and risky.

Partition valid flag error fault

There is also an important part in the Main Boot Sector of the hard disk, that is, the last two bytes: "55aa", which is a valid symbol of the sector. When the disk is started from a hard disk, floppy disk, or disc, the two bytes are detected. If the disk exists, the hard disk exists. Otherwise, the hard disk is not recognized. This can be used for the encryption technology of the entire hard disk, and the debug method can be used for recovery. In addition, when the DOS boot sector does not have a boot flag, the system starts to display "mmissing Operating System ". The convenient method is to use the following common repair methods for the dossystem.

Startup Fault Caused by DOS boot System

The dos boot system consists of the DOS Boot Sector and the DOS system file. System files mainly include IO. sys, msdos. sys, command. com, where command. com is a DOS shell file, which can be replaced by other similar files, but is a required file for DOS Startup by default. In Windows 95, msdos. sys is a text file that is required to start Windows, but does not need to be used when only DOS is started. When a DOS boot error occurs, you can boot the system from a floppy disk or a CD and use the Sys C: Command to transfer the system to fix the fault, including the Boot Sector and system files.

Read/write failures caused by fat tables

The fat table records the storage address of the hard disk data. Each file has a set of fat chains to specify the address of the cluster to store. Corruption of the fat table means the loss of file content. Fortunately, the DOS system provides two fat tables. If the current fat table is damaged, the second fat table can be replaced. However, because the length of the fat table of disks of different specifications and the address of the second fat table are not fixed, you must find the correct position in the fix, some tool software such as Nu has such repair functions and is very convenient to use. Debug can also be used to achieve this operation, that is, use its m command to move the second fat table to the first table. If the second fat table is damaged, the hard disk cannot be restored to its original state, but the file data is still stored in the data area of the hard disk, you can use the chkdsk or Scandisk command to fix the issue *. chk file, which is the loss of the sector data of the fat chain. If it is a text file, you can extract the complete or part of the file content from it.

Guide Fault Caused by directory Table Corruption

The directory table records the file name and other data in the hard disk. The most important one is the starting cluster number of the file. Because the directory table does not have the automatic backup function, a large number of files will be lost if the directory is damaged. One way to reduce the loss is to use the chkdsk or Scandisk program to restore the method, search for * from the hard disk *. chk file, because the directory table is damaged, only the first cluster number is lost, each *. the chk file is a complete file. Change it to the original name to restore most files.

Data Recovery during accidental deletion of partitions

After the hard disk partition is deleted using fdisk, the data on the hard disk disappears completely. When the hard disk is not formatted, it is displayed as an invalid drive. If you understand how fdisk works, you will know that fdisk only rewrites the content in the primary Boot Sector of the hard disk (0-sided 0-Sector 1-sector). Specifically, it deletes the partition table information of the hard disk, the data in any partition on the hard disk has not changed. You can recover the original partition and data by following the preceding solution to partition table errors. If you have already formatted the partition, you can restore the partition data in the following way after the partition is restored.

Recover accidentally formatted Hard Disk Data

In a high version of DOS, the format formatting operation creates disk information for restoring formatting by default, in fact, the DOS Boot Sector, FAT partition table, and directory table of the disk are copied to the last several sectors of the disk (because the following sectors are rarely used ), the content in the Data zone has not changed at all. In this way, you can run the unformat command to restore it. In addition, DOS also provides a miror command to record the information of the current disk for restoration after formatting or deletion. This method is also effective.

Hard Disk Partition recovery and backup

You will always feel the importance of Hard Disk partitioning. It is true that the status of Hard Disk partitioning is unquestionable, so it has become the target of many virus attacks. In addition, unexpected situations, such as sudden power outages, can also cause data loss in the primary boot partition of the hard disk. If the partition is damaged, the system immediately becomes paralyzed and cannot be moved. Therefore, the partitioning restoration and backup techniques must be mastered:

First, if the computer cannot detect the hard disk and the hardware problems are eliminated, we should start to check the partition. In general, if one of the primary boot area, boot program, or partition table is damaged, the hard disk will be lost. One by one:

Check and repair Partitioned Tables

If the computer cannot be started from the hard disk, we can try to access the hard disk after the disk is started. If the hard disk can be accessed, it means that the operating system is damaged. You can reinstall the operating system to restore it, or directly copy the hard disk on another computer; if you cannot access the hard disk, it may be that the boot area of the primary boot area or the boot area of the bootable partition is damaged. At this time, we can use DEBUG or tools such as Norton disk editor to check whether the Master Boot area of the hard disk is normal. The following is an example of using debug to access the main boot zone: (XXXX indicates the memory segment address, because the bios, operating system, and configuration file of the computer are different ), as a result, the XXXX address segment is different)

A:> debug

-A Assembly command

XXXX: 0100 mov ax, 201 read a sector

XXXX: 0103 mov BX, 600 read to section 0600 of the current segment

XXXX: 0106 mov CX, 1 cylinder number = 1

XXXX: 0109 mov dx, 80 head number = 0, drive number = 80

XXXX: 010c INT 13 disk read/write interrupted

XXXX: 010e INT 3 breakpoint interrupt

XXXX: 010f

-G: Execute the preceding command.

-D 600 displays the content of the primary boot Area

If the primary boot area is correct, check whether the boot program and partition table are normal. If a program exception is found (compared with a normal program), it indicates that the Bootstrap program may be disturbed. There are many methods to restore the boot program. First, we will introduce the manual recovery method: First, you must obtain the file mboot stored in the master boot area from a normal computer. dat, after starting with a floppy disk, run the debug program and enter the following command:

-N mboot. DAT: Read the file mboot. dat.

-1 800 read to the current segment 0800

-M 7Be 1 40 9be: copy the original Partition Table to the normal primary boot Area

XXXX: 0100 mov ax, 301 write 0800 pieces of data back to the Boot Sector

XXXX: 0103 mov BX, 800

XXXX: 0106

-R ip Address: modify the current instruction pointer

IP: 010e 0100 the current Instruction Pointer Points to 0100

-G execution

Remember, it must be exactly the same hard disk partition table. If it cannot be obtained, you can use software such as diskedit to manually enter the partition table for restoration.

Use tool software to restore boot partitions

In addition to manual recovery, there are many specialized tools and software available to restore and back up the boot zone of the system.

Fixmbr: This is a DOS-based application software. Its main function is to reconstruct the primary Boot Sector. This software only modifies the record of the primary Boot Sector and does not write to other sectors. The basic command format is as follows:

Fixmbr [Drive] [/A] [/d] [/P] [/Z] [/h]

/A active DOS partition (activate basic DOS partition)

/D Display MBR (displays the content of the Master Boot Record)

/P display partition (display the DOS partition structure)

/Z zero MBR (resetting the primary Boot Record zone)

/H help (help information)

If you type fixmbr directly and press enter, the MBR structure check will be performed by default. If the system is abnormal, the system prompts whether to fix the problem. Answer/"Yes/" and search for partitions later. After the corresponding partition is found, the system will prompt whether to modify the MBR. If yes, the repair will begin .. If the search result is incorrect, but the/Z toggle is used, restarting the system will return to the original state.

In addition to fixmbr, kv3000 is a antivirus software, and it also has a very strong partition repair capability. What's even more exciting is that it can also back up system partitions. In this way, even if all the two partition tables on the hard disk are damaged, we can use the Partition Table backed up on the floppy disk for repair. Let's talk about the kv3000 backup. Enter the following command format (kv3000/B or kv3000/hdpt. dat), a virus-free Master Boot information file is automatically backed up to disk A, and its names are hdpt. dat and hfboot. dat. When the Hard Drive boot information is damaged by viruses or the Master Boot Record is damaged, enter/"kv3000/hdpt. dat/"to restore the backup content to the hard disk (the backup must be the same as the hard disk to be restored ).

If you have not performed a backup, kv3000 also allows you to repair the Master Boot information of the hard disk, then run kv3000, and press the F6 key to view hidden sectors of the hard disk that are no longer bootable, you can check whether the Master Boot information of the hard disk is normal. If no key code is found in the 0-side, 0-column, and 1-sector of the hard disk, the hard disk itself cannot be self-guided, even after the floppy disk is booted, it cannot enter the hard disk. You can find it in the hidden sector of the hard disk. After finding it, the system will flash red/"80/" and/"55aa/" in the table, and give a sound to remind you, the following line of message appears:/"F9 = save to side 0 cylinder 0 Sector 1 !!! /". At this time, click the/"F9/" key to overwrite the primary boot information of the original hard disk to the zero-side, zero-column, and one-sector hard disk. Then, the computer will reboot the hard disk to restore the Startup Performance of the hard disk, and the hard disk can also be accessed after the floppy disk boot.

In addition, if the Hard Disk Master Boot Record and partition table are damaged due to virus damage or operation errors, the hard disk cannot boot or the floppy disk cannot boot into the hard disk, if the Master Boot Record is backed up on a floppy disk with the kv3000/B command, kv3000/hdpt is available. The dat command then restores the Hard Disk Master Boot Record. If you have not previously backed up the hard disk master boot information, you only need to use kv3000 to quickly recreate the hard disk partition table.

After the floppy disk directs the system, run kv3000. After the main menu is displayed, press the F10 key to quickly test system parameters and hard disk partition tables. If the hard disk partition table is abnormal, kv3000 saves the bad partition table to a floppy disk, and then automatically recreates the hard disk partition table to bring the hard disk back to life.

If the hard disk has only one partition and the file allocation table (fat table), the root directory (root table) of the file has been severely damaged by viruses, even if the Partition Table of drive C is recovered, you cannot use drive C boot. You need to use other dedicated repair software to restore data. However, if there are other extended partitions, such as D and E, kv3000 can normally retrieve the partitions that have not been destroyed, recreate a new hard disk primary partition table, and then, use a DOS system floppy disk to guide the computer and then enter the D and E partitions of the hard disk.

Common Fault Analysis and troubleshooting for hard drive failures

As the most important storage device of a microcomputer, hard disks play an important role in the microcomputer system. If the hard disk cannot be started, it will cause you to be in a hurry. Here we will introduce you to several "weapons" to specifically deal with the "stubborn" problem that hard disk cannot be started. You must be careful when using them. Otherwise, if the hard disk is damaged, the silver will be wasted!

Fault symptom 1: After the device is started, the screen displays "device error/" and "non-system disk or disk error, replace and strike any key when ready /", the hard disk cannot be started. After the disk is started with a floppy disk, enter "C:" After a: //>. The screen displays "invalid drive specification/". The system does not recognize the hard disk.

Fault Analysis and Handling: the cause of the fault is generally caused by the loss of hard disk setting parameters in CMOS or incorrect hard disk type settings.

Go to CMOS and check whether the hard disk setting parameters are lost or whether the hard disk type is set incorrectly. If this is the case, you only need to restore or modify the hard disk setting parameters. If you forget the hard disk parameter, you can also use the backed up CMOS information for recovery. If you have not backed up the CMOS information, do not worry. Some high-end microcomputer CMOS settings include "HDD Auto Detection/" (automatic hard disk detection) option to automatically detect the hard disk type parameters. If this option is not available, you have to open the chassis, view the hard disk parameters on the hard disk surface label, and modify the parameters accordingly.

Fault symptom 2: After the instance is started, "Wait/" prompts you to stay for a long time, and "HDD controller failure/" appears at the end /".

Fault Analysis and Handling: the fault is generally caused by poor contact with the hard drive line interface or wrong wiring. Check the connection between the hard disk power cord and the hard disk, and then check the connection between the hard disk data signal line and the multi-function card or hard disk. If the connection is loose or the connection is reversed, the above prompt will be displayed, it is best to find a computer with the same model and normal use. You can compare the connection of the cable. If the cable is reverse, it will be clear at a glance.

Fault symptom 3: After the boot, the screen displays "invalid Partition Table/". The hard disk cannot be started. If the disk is started from a floppy disk, the C disk is recognized.

Fault Analysis and Handling: the cause of the fault is generally that the partition table in the hard drive Master Boot Record has an error. When multiple auto-cited partitions are specified (only one auto-lifted partition can exist) or when the virus occupies a partition table, the above prompt is displayed.

The Master Boot Record (MBR) is located in the 0 head/0 cylinder/1 sector and is generated when fdisk. EXE partitions hard disks. MBR consists of three parts: the Main Boot Program, the partition table, and the ending sign 55aah, which occupy a single sector. The main boot program contains the program code, error information, error handling, and other content for checking the hard disk partition table. When the hard disk is started, the main Bootstrap will check the auto-lifting flag in the partition table. If a partition is a custom partition, it indicates 80 h. Otherwise, it is 00 h. The system requires that only one partition be a custom partition, if the partition table contains multiple auto-raising marks, the primary Bootstrap will prompt "invalid partion table. The simplest solution is to use NDD to fix errors in the partition table. If an error is found, you will be asked if you are willing to modify the error. You only need to continuously answer yes to correct the error, you can also use the partitioned table that has been backed up to overwrite it (kv300 and rescue in nu8.0 all have the function of backing up and restoring the partitioned table ). If the partition table is infected with virus, the problem cannot be solved by formatting. You can use anti-virus software and NDD to fix the problem.

If none of the above methods can be solved, another way is to use fdisk to re-partition, but the partition size must be the same as the original partition. This is especially important. Do not perform advanced formatting after the partition, then use NDD to fix the problem. The recovered hard disk can be started, and the information on the hard disk will not be lost. In fact, using fdisk partitioning is equivalent to overwriting the original partition table with the correct partition table. This trick is especially effective when the hard disk is not recognized after a floppy disk is started.

Fault symptom 4: After the system is started, the self-check is completed, and the hard disk crashes or the screen displays "no rom basic, system halted /".

Fault Analysis and Handling: the cause of the fault is generally caused by damage to the boot program or virus infection, no self-lifting mark in the partition table, or the end mark 55aah is rewritten. Start from a floppy disk and run the command "fdisk/MBR. Fdisk contains the main boot program code and the ending sign 55aah. With the above command, the correct primary boot program and ending sign in fdisk can overwrite the primary boot program on the hard disk, this action is fast and flexible for fixing the master boot program and ending sign 55aah damages. NDD can be used to quickly recover a fault that does not have a self-lifting flag in the partition table.

Fault description 5: After the instance is started, the system prompts "error loading operating system/" or "missing operating system/" appear on the screen.

Fault Analysis and Handling: the fault is generally caused by an error in the DOS Boot Record. The dos Boot Record is located in the logic 0 sector and is generated by the advanced format command. After checking that the partition table is correct, the main Bootstrap program reads the DOS Boot Record Based on the start address of the DOS partition specified in the partition table. If five consecutive reads fail, the error message "error loading opearting system/" is displayed. If the DOS boot record can be correctly read, the main boot program sends the DOS Boot Record to the memory at 0: 7c00h, then, check whether the last two bytes of the DOS Boot Record are 55aah. If not, the message "missing Operation System/" is displayed. You can fix it with NDD. If it fails, you have to use the format C:/s command to overwrite the DOS Boot Record. Maybe you will think that the data on drive C will be lost after formatting. In fact, you don't have to worry about it. The data is still stored on the hard disk, after the drive C is formatted, unformat in nu8.0 can be restored. If you have used the mirror in the doscommand or the image program in nu8.0 to create an image file for the hard disk, the hard disk can be completely restored. Otherwise, all files in the root directory of the hard disk are lost, the first sub-directory name under the root directory is changed to dir0, dir1,

Dir2.... but the files under the level-1 subdirectory and their sub-subdirectories are intact. As for the files lost under the root directory, you can use the unerase in nu8.0 to restore them.

To sum up, the failure to start a hard disk is mostly caused by the error of the Master Boot Record, DOS Boot Record, and three hidden files on the hard disk, therefore, we need to develop a good habit of backing up the Master Boot records and DOS boot records, so that the problem can be solved smoothly at critical moments.