Once in Win7 safely uninstall U disk after reinsert, found that win 7 but can not recognize this U disk. And then you have to reboot your computer to recognize it again. Here's how to solve this problem:
First click Computer in the Windows 7 desktop mouse Right-click and choose Properties. Then click the Device Manager in the upper left corner, in the Device Manager window that pops up, click Expand Universal Serial Bus control, there will be many "USB Root hub" Devices list, then right-click each "USB Root hub", select the "Disable" menu, and then "Enable."
With each USB Root Hub operating like this, Windows 7 can recognize the U disk again without rebooting.