Disable /Enable USB Ports

"Warning : Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method."

Just  follow these simple  steps

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then click OK.
3. Locate, and then click the following registry key:  
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UsbStor
4. In the right pane, double-click Start.
5. In the Value data box, type 4,in place of 3, and then click OK.
6. Quit Registry Editor and plug any USb device to see effect.