Restart the computer to identify the reason for the U disk:
one, the USB port voltage instability caused by: First restart the computer, delete u disk drive, and then insert. You can find a U disk.
second, the system instability caused by: The reload system is a solution, but to get the other computer replication will be faster.
third, motherboard and system compatibility issues: This type of failure is the most well-known is the NF2 motherboard and USB compatibility issues. If you encounter this problem on the NF2 motherboard, you can install the latest NFORCE2 dedicated USB2.0 drivers and patches, the latest motherboard patches and operating system patches, or not, try refreshing the motherboard BIOS can generally be resolved.
system or BIOS problems: When you disable USB in the BIOS or operating system, USB devices cannot be identified in the system. The workaround is to turn on the options associated with the USB device. is the boot press F2 or DEL key, into the BIOS, the Enable USB device select Enable.