At this point there appears to be nothing wrong with it. Your computer sees it and assigns a drive letter in Explore, right? Windows is telling you that there is no data on the disk to read because it is not formatted; since it tells you it is RAW space there is not even a partition set to put data in. If the partition became corrupted you would get a message, "partition unreadable possibly corrupted" or something to that effect. At this point there is nothing for XP to recognize. Let's try a couple of things:
>Enter Disk Manager
r in Administrator Tools
and view all the drives posted there; what information does it give you on your USB external drive? Does it give you the file structure, partition size, active or inactive, healthy, anything at all?
, click on the DOWNLOADS tab, and download the ISO and burn to a CD Seatools for DOS
; insert it in your CD drive and reboot. Seatools for DOS will load; select your USB drive, and click "Short scan" at the upper left menu and let it complete. It will give you a PASS or FAIL message. If FAIL, the drive is bad.
and download the ISO of Reatogo; burn to a CD and reboot with it in the drive. Be patient, it takes a long time to load. Once loaded, you will see a familiar XP screen, find your USB external drive and click on the icon; check if you can see your data listed. If it gives you an error message that means there is no data to read.
Please post back with the results of each test I listed above.