|"Can the unlicensed copy of XP disable an external drive?"|
NO, unless you can't get into Windows.
Problems with USB drives are COMMON.
Usualy the problem is either
- you need to plug it into a different USB port in order for it to be detected properly,
- or - it is being detected but it doesn't show up in My Computer because you have damaged data on the drive by unplugging it while Windows was running without using Safely Remove Hardware to STOP accessing the drive.
Troubleshooting USB device problems including for flash drives, external drives, external memory card readers.
See Response 1:
External optical drives also require 500ma from the USB port you plug it into.