External USB Hard Drive Not Recognized in XP?

Help anybody,

My laptop HD burned up and I got a new one but the old one was under warranty so I bought a drive enclosure for $20 and use it as a backup drive of 80Gig. The enclosure came with a USB connection, etc. It used to work (come up automagically when I would plug it in), but I had some work done on the laptop at CompUSA and now when i plug in the USB cable it says Unknown Device.

I’ve scanned for hardware changes, tried to use other Toshiba drivers but no joy. How do I get XP to recognize the drive???

Thanks,
Dave