What if the computer cannot recognize the USB flash drive?

 

What should I do if my computer cannot recognize the USB flash drive?

Right-click my computer and select "manage" from the shortcut menu to open the "Computer Management" window. In the computer management window, select disk management under "Storage". If you can see a USB flash drive without a drive letter, right-click the USB flash drive, select the "Change drive name and path" option to enable "change ...... The drive letter and path dialog box. Click "change" to open the "Change drive letter and path" dialog box. In the drop-down list on the right of "specify the following drive letter, select the drive letter you want to assign to the USB flash drive, and select the drive letter as far as possible, such as X, Y, and Z. After selecting the drive letter, click OK to return to the last "change ...... In the "drive letter and path" dialog box, click OK again to return to the "Computer Management" window. At this point, if everything is normal, a long-lasting drive letter is set for the USB flash drive, but it is not affected by the Virtual Drive.

Suggestions

Insert the USB flash drive to your computer and check whether the icon is displayed in the taskbar. If yes, right-click my computer and choose Properties> advanced> hardware> Device Manager to check whether there are any devices with question marks, right-click the question mark on the device-update the driver and next-No temporarily not connected to the network-next step to automatically install the software (recommended ).

In addition, the system does not recognize the USB flash disk.

1. Disable the motherboard USB device.

The Administrator disables the USB device in the CMOS settings and sets the BIOS password, so that the computer will not recognize the USB flash drive after it is inserted into the computer. This method has its limitations, that is, it not only disables the USB flash drive, but also disables other USB devices, such as USB mouse and USB Optical Drive. Therefore, this method is generally not used by administrators, unless the computer is very important, it is worth it to discard the entire USB bus function. However, such blocking can also be cracked, even if a password is set. The entire BIOS settings are stored in the CMOS chip, and the memory of COMS is powered by a capacitor on the motherboard. Capacitor power comes from the motherboard battery, so as long as you unload the motherboard battery, with a wire to the original battery place is short and the negative pole, instantly can clear the entire CMOS settings, includes the BIOS password. Then, you only need to unmount the battery and reset the CMOS to use the USB device. (Of course, this requires the chassis to be opened. Generally, it is not suitable for many users ~~)

2. Modify the registry key to disable USB mobile storage devices.

Open the Registry file, expand "HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ usbehci", double-click the "Start" key on the right, and change "value data" in the editing window to "4 ", select "hexadecimal" as the base number. After modification, log out and you will be able to see the effect. To prevent others from using the same method, we can delete or rename the Registry Editor Program.

Tip: the "Start" key is the work switch of the USB device. The default value "3" indicates manual, "2" indicates automatic, and "4" indicates disabled.

3. Disable the permission to use removable storage in Computer Management. Computer Management is a Windows Management component that can be opened on the control panel-management tools-Computer Management. In the tool window, general items in storage -- removable storage -- property can control whether the system tray displays security, and manage the permission to use mobile storage devices. In security, the general user's permission is reduced to disable the USB flash drive. The method of cracking is also very simple. The administrator can reduce the permission of ordinary users to use mobile storage devices, but the permission of computer management may not be disabled. Common users can use this tool to remove the permission restrictions for using USB mobile storage devices. In addition, it is worth mentioning that if a USB flash drive can be driven after it is inserted into a computer, but there is no drive letter in my computer, it is likely that the Administrator has changed the default drive letter of the USB flash drive, this makes my computer unrecognizable. In this case, you can see the USB flash drive in movable storage. You can re-allocate a drive letter to the USB flash drive in the USB flash drive attribute settings, and re-plug the USB flash drive once. Then you can see the drive letter on my computer.

1. First, you can switch the USB flash drive to another machine to see if it works properly. If the possibility of hardware damage is ruled out, it is generally caused by software problems. In the Windows XP + SP1 operating system, some USB devices often encounter unstable operations. You can try to install the USB driver that comes with the device. In addition, it is best not to use USB extended cables to prevent instability due to insufficient power supply. If it still does not work, you can set the USB interface to USB transmission rate in the BIOS settings of the motherboard.

2. Start the computer (for Win98), enter the BIOS settings of the motherboard, and check whether the USB related options in the BIOS are enabled: onchip USB is set to enabled; USB controller is set to enabled; set pnp OS installed to yes; assign IRQ for USB to enabled.

To use a USB device normally, you must first enable the USB interface. You can do this in the BIOS of the motherboard. Generally, you only need to enter the chipset features settings in the BIOS, set the USB keyborad/mouse legacy option to enable to ensure that the USB keyboard is used in the operating system. These options enable the Motherboard chipset to fully support USB devices and prepare for System Identification of USB devices.

Iii. Poor USB port access

Solution: Unplug and wait for 10 seconds before plugging in the USB port to keep the contact intact;

5. The flash drive driver is not installed successfully (in Win98)

Solution: click "my computer", select Properties, find "Universal Serial Bus", delete the USB Mass Storage items, and click "refresh ", then follow the prompts to reinstall the driver.

6. other USB devices (such as scanners, printers, and digital cameras) can be used normally. The flash indicator is not on when the USB flash drive is connected, and cannot be used.

1. Check whether the USB flash drive is connected to the computer and use another USB interface for testing.

2. Check the Device Manager to see if the "general bus device controller" entry exists. If not, enable the USB interface entry * in the BIOS of the computer motherboard ).

3. If other USB devices are installed on your computer, uninstall the driver and install the USB flash drive first.

4. Try this USB flash drive on another computer and check whether the USB flash drive is poor.

7. Boot is not supported by the boot-type USB flash drive on the computer. It may be not supported by the motherboard model.

How to determine whether a motherboard supports the Flash Drive boot System

The USB flash drive and USB hard drive are simulated to boot the computer. As long as the computer motherboard supports USB device boot, that is, BIOS boot options include USB-FDD, USB-HDD or other similar options, you can start the computer with a boot optimized disk.

8. The first time I used the USB flash drive on my computer, I did not see a prompt to find a new hardware window. The reason why the driver cannot be installed may be:

1. the motherboard USB controller is not enabled

Solution: Enable this feature in the BIOS of the Computer Board.

2. the USB controller is enabled but is not running properly.

Solution: Delete and refresh Related Devices under universal serial controller in Device Manager.

3. Why is the USB flash drive yellow in the Device Manager when it is identified by a computer? Or! Other devices or unknown devices ".

Solution: Delete the device and refresh it.

9. A large USB flash drive (such as a USB flash drive with MP3 player or recording functions) or a mobile hard disk cannot be used properly on a computer. Although the system prompts that an unknown USB device has been found, however, the USB flash drive or mobile hard drive cannot be correctly identified.

The reason may be:

1. Insufficient power supply for the USB interface: The system allocates a maximum output current of 500mA for each USB interface. Generally, the USB flash drive only requires 100mA of the operating current, so no problem occurs during use. Most mobile hard disks use an ordinary 2.5 inch hard disk, and the operating current is between 500mA and ~ 1000mA, if the power supply is only through the USB interface, when there is no other USB device in the system, it can still be barely used, but if the voltage is unstable, the problem of insufficient power supply may occur at any time. Especially when using a mobile hard drive that supports USB 2.0, the situation is the most serious. In addition, if your laptop is powered by a battery, the USB interface will allocate less power.

2. using an external USB expansion card: when using a USB 2.0 USB flash drive or a mobile hard drive in a laptop, if the laptop does not support USB 2.0 technology, generally, the PCMCIA card must be used to convert the USB 2.0 expansion card for indirect support. These expansion cards basically use the d720100agm USB control chip of NEC, and provide two USB 2.0 interfaces if there is less, five USB 2.0 interfaces are provided, which is sufficient for general users. Because the power provided by the pcmica interface is smaller than that of the on-board USB interface, the operation of the mobile hard disk may fail due to insufficient power supply.

Solution:

1. It is connected to one end of the mobile hard disk from the USB connection line and leads to a adapter line, which can be plugged into the PS/2 interface behind the computer to power up, which can provide a larger current output than the USB interface.

2. with the power compensation line (also known as "keyboard power cord"), if the USB flash drive or mobile hard drive box provides an optional power adapter, you can directly use the external power supply, in this way, we can fundamentally avoid the problem of insufficient power supply.