FOR ENABLING
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_MACHINESYSTEMCurrentControlSetServicesUsbStor
4. In the details pane, double-click Start.
5. In the Value data box, type 4, click Hexadecimal (if it is not already selected), and then click OK.
6. Exit Registry Editor.

FOR DISABLING

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_MACHINESYSTEMCurrentControlSetServicesUsbStor
4. In the right pane, double-click Start.
5. In the Value data box, type 3, click Hexadecimal (if it is not already selected), and then click OK.
6. Quit Registry Editor.