Hard drive "logical lock" solution _dos/bat

Many computer users have seen or heard that, when the so-called "logic lock" on the hard disk, whether it is a floppy disk, hard disk, or CD-ROM can not start some computers. So what exactly is a "logical lock"?
The so-called "hard drive logic lock" is made by using a certain DOS error. It uses the "cyclic partitioning table" technology, so that some of this error dos can not be started with any device, including floppy disk and other mobile devices. When DOS starts, the system will automatically search the hard disk of the various partitions of information, such as type, size, etc., so that the system can identify the hard drive, respectively, assigned to C, D, E, F and other drives, and enable users to carry out a variety of operations. and "logical lock" is the use of this point, by modifying the partition table of the hard disk to make the partition table loop, that is, the first logical disk of the extended partition point to itself, so that some DOS system start to find the partition occurs when the cycle of death loop and can not start.
Visible, this is actually a DOS boot error caused by. It is said that as early as 1992, an anti-virus expert named Mike discovered the problem and reported it to the manufacturer of DOS with this problem, such as IBM, who manufactures Pc-dos, Novell, who manufactures Dr-dos/novelldos, and Microsoft, which produces MS-DOS. Soon after, IBM, Novell and other companies have announced that a new version of its DOS has completely resolved the problem, only MS-DOS Microsoft ignored, resulting in a new version of MS-DOS, such as 6.x, 7.x and so on continue to exist.
However, Microsoft's MS-DOS is the most widely used, so its impact and harm is greatest. Once the user's hard drive is locked by a "logical lock", various Microsoft operating systems, such as MS-DOS 5.x/6.x/7.x/8.0 boot disks, fail to start, creating a false image of a hardware malfunction, and even a lot of the pros are helpless. Because this is very scary, will lead to computer can not be used, so many people have to find ways to prevent and solve. In fact, it is not difficult to solve, the following describes several solutions.

* Start with non-MS-DOS operating system

As you can tell, the "Hard drive logic lock" mainly affects Microsoft's MS-DOS system, so it's OK to use another DOS boot. To this end, I purposely made a "logical lock" on the hard disk for several of the more useful versions of DOS, such as MS-DOS 7.10, Pc-dos 7.10, Dr-dos 7.05, Rom-dos 7.10, FreeDOS beta9, Pts-dos Pro 2000 's boot disk , the results of the start test are as follows:

Pc-dos 7.10 Startup disk: Start all normal;
Dr-dos 7.05 (Version number: 7.10) Startup disk: Start all normal;
Rom-dos 7.10 Startup disk: Start all normal;
FreeDOS beta9 (Version number: 7.10): When starting to display the hard drive error, and completely normal start;
Pts-dos Pro 2000 (version No: 6.90): Start all normal.

Note: All the above DOS are very stable, and both support FAT32 partition and large hard drive, where Rom-dos 7.10 also fully local support long file name, and very good compatibility.

As a result, you can start a hard drive with a "logical lock" with any of the above DOS boot disks, and the disk characters (such as C:) of the hard drive that have been locked after startup are not visible, but various disk partitioning software, such as Norton Disk Editor 2002, Norton Disk Doctor 2002, as well as DOS from the Fdisk program, and so on, can show the locked hard drive, at this time, the above mentioned Diskedit and other tools for this hard disk to view/manual repair operations, can also use some software for automatic repair, such as Netresq, Srctools, To completely remove the "logical lock" on the hard drive, and the data on your hard disk will not be damaged.

* Start with a repaired MS-DOS boot disk

Although the MS-DOS boot disk is not in normal condition to start the computer while the hard drive is locked, since this is only a bug in MS-DOS's startup file Io.sys, fixing this bug,ms-dos boot disk will not be affected by a "logical lock" to start properly. However, you should use the correct method even if you are fixing bugs. It has been mentioned that by modifying the hard disk partition Mark "55AA" in the Io.sys, this method is very bad. Because this method is actually let Io.sys completely ignore the existence of the hard disk, that is, by skipping the hard disk to start the floppy disk, so that regardless of whether the hard drive is locked, the hard drive can not be recognized with this boot floppy, so this boot disk can not be used as a normal MS-dos boot disk. Conversely, if you fix bugs in Io.sys in the right way, after booting with this floppy disk, if the hard drive is good, it can be recognized properly, and even if the hard drive is locked by a "logical lock", it can also be used as mentioned in the above method (that is, "start with a non-MS-DOS operating system") using Pc-dos, Dr-dos, Rom-dos, FreeDOS, Pts-dos Pro, and so on start the floppy disk after the start of further repair operations. Some of the lower versions of MS-DOS, such as the version 3.2 boot disk, were also mentioned to start the computer. But this is obviously a lot of shortcomings, one is that the old version of DOS is difficult to find, the second is because its version is too low, the function is very few, the compatibility is also very poor; third, these low versions of DOS themselves do not support large hard drives (even 32M does not support), logical partitions, and so on, even the hard drive caused real damage, and, MS-DOS 3.2 And so on, even 1.44M floppy disk does not know. As you can see, a lower-version MS-DOS startup method is not quite feasible. Therefore, it is important to use a good method to correct bugs in the high version of MS-DOS Io.sys. Take the MS-DOS 6.x boot disk as an example, just use any 16-in-editor (such as PCTools, etc.) to find the 16-string "07 72 03" In the Io.sys file and replace the last "03" with "06". Other versions of MS-DOS can use similar methods, such as the io.sys of MS-DOS 7.10, see "China DOS Alliance Forum". As a result, Microsoft's MS-DOS boot disk can be started normally in the same way as any other DOS when the hard drive is locked by a "logical lock".

The method mentioned above is the most direct way to solve the "hard Drive Logic lock" (that is, "start the computer using a DOS boot disk that is not affected by the ' logical Lock"), and is the best way. Therefore, just make one of the above mentioned boot disks (such as Pc-dos 7.10 boot disk, Rom-dos 7.10 boot disk, FreeDOS boot disk, or repaired MS-DOS boot disk, etc.). This boot disk can be used as a normal startup disk at ordinary times, and can be started and resolved when the hard drive is locked.
Others mentioned other "methods", such as hard drive hot plug, DM low grid, and so on, not only troublesome, dangerous, but also can damage all the data on the hard disk. For example, after the hard drive hot plug (need to remove the chassis and take down the hard drive, and then reload the hard drive after the boot, very troublesome and dangerous), even if the floppy boot successfully, at this time the hard disk will not be completely recognized, including a variety of hard disk tools can not recognize. If you skip the BIOS to the hard drive with DM, all data on the hard drive will be lost, unrecoverable, and very costly. Thus, hard disk hot Plug and so on "methods" are not practical or feasible.

Therefore, as long as found a good solution, and the corresponding operation, the so-called "hard disk logic lock" can be easily resolved, we may wish to try.