USB is not recognized by the computer, if it is the system or system driven by the reasons, you can repair the following methods:
1, the boot press F8 into Safe mode after the exit, select Restart or shutdown in the boot, you can enter the normal mode (repair the registry).
2, if the failure is still, please use the system with the System Restore, restore to you did not appear this time of failure repair (if normal mode recovery failure, please turn on the F8 into Safe mode to use System Restore).
3, if the failure is still, using system disk repair, open a command prompt input Sfc/scannow return (SFC and/between a space), insert the original system disk repair system, the system will be automatically compared to repair.
4, if the failure is still, set the optical drive in the BIOS for the first boot device Insert system installation disk press R to select "Repair Installation" can be.
5, if the failure is still, it is recommended to reload the operating system.
U disk inserted into the computer, the computer prompts "unrecognized device" Troubleshooting methods are as follows:
1th step: if u disk insert computer, computer prompts "unrecognized equipment", the U disk power supply circuit is normal. Then check the USB connection circuit failure of u disk.
2nd step: if u disk USB interface circuit is normal, it may be a clock circuit failure (U disk clock frequency and computer can not be synchronized). Then detect the crystal oscillator in the clock circuit and harmonic vibration capacitance.
3rd step: If the clock circuit is normal, it is the main control chip poor work. Detection of the main control chip power supply, if the power supply is normal, then the main chip damage, replacement can be.
There is also a reason is that the USB interface is not enough power, may be the USB interface attached to too many peripherals caused by insufficient power. It is recommended that you use a live Usbhub or a PS/2 adapter using a USB switch. It is also possible that Windows XP by default to open the power-saving mode, resulting in insufficient USB interface, so that the USB interface intermittent failure. Right-click My Computer/Properties/hardware/Device Manager, double-click the Universal serial Bus controller to several "USB Root Hub" to double-click on any one, open the Properties dialog box, switch to the Power Management tab, remove the "allow the computer to turn off this device to save power" before the check, click OK to return, Restart the computer after you have modified the properties of each USB Roothub in turn. USB device can restore stable operation, the frequency as low as possible.
If there is a letter but not shown, the workaround:
Right-click My Computer/management/storage/Disk Management, then right-click the removable disk icon, click the Change Drive and Path option on the shortcut menu, and click the Add button in the subsequent interface, then select Assign Drive letter and select the appropriate letter from the Drop-down list next to the option. You can click OK. When I finally open my computer, I can see the drive letter of the removable hard disk.
The above is about inserting U disk after the computer will crash the diagnosis and resolution of a variety of countermeasures, U disk used a long time will inevitably encounter a variety of problems, we need to be careful to protect the U disk and find solutions, so that we can make this practical small partner with us longer oh.