This trick is for all those who wanna use the USB port on their office PC. The trick works only on Windows XP SP2
To disable usb storage devices:
Now in the right hand side panel double click start and set its value to 4.
To enable usb storage devices:
Double click start and put its value to 3.
Navigate through HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
Double click on WriteProtect from the right panel and change its value to 0(zero).
To enable read only policy put the value as 1 instead of 0.
Warning: Messing up with regedit might lead to re-installation of Windows.