Windows 7 Professional doesn't mount my usb flash drive anymore

Remove the INFCACHE.1 file, Perform the following steps to remove and rebuild the INFCACHE.1 file.

1. Disconnect all USB deviced except the keyboard and mouse. (Desktop only) (Laptop remove all usb devices)
2. Open Windows Explorer by right clicking on Start, and then clicking on Explore.
3. In the address bar, type

   C:\Windows\System32\DriverStore

4. Locate the INFCACHE.1 file, right click on it, and then click Properties.
5. In the INFCACHE.1 Properties dialog box, click the Security tab, and then click Edit.
6. In the User Account Control dialog box, click Continue.
7. In the Permissions for INFCACHE.1 dialog box under the Group or user names section, click Add.
8. In the Select Users or Groups dialog box in the Enter the object names to select text box, typeAdministrators, postfixed with a 's', and not only Administrator. If you only choose theAdministrator account you will not be able to delete the file. After that, click OK.
9. In the Permissions for INFCACHE.1 dialog box in the Permissions for Administrators section, select to allow Full Control, and then click OK.
10. In the INFCACHE.1 Properties dialog box, click OK.
11. In the Windows Explorer window, delete INFCACHE.1, before deleting it, you can make a backup copy of this to another folder of you wish.
12. Connect a USB device other than the one that Windows had trouble detecting. This forces Windows to rebuild the INFCACHE.1 file.

Note: This detection issue can happen several times in a row. If so, repeat steps 1-12 until the device is detected.