As you are probably aware, most external USB drives are automatically
recognized by XP, without the need for any extra drivers.
In this case I would be worried that the external drive is bad.
Try plugging it into a different PC, also running XP. If that works, then
there is something odd about the first PC. Perhaps, try a different USB
port? Also, try a different USB device. Can the first PC see anything USB?
If necessary, use the XP device manager to uninstall the USB port itself
(with the drive not attached), then use the same device manager to detect
new hardware, and hopefully fix the USB port. This is obviously a software
fix, not a hardware fix.
But, if the USB drive fails on two computers, then it is likely the drive.
The one other possibility is the USB cable. Don't laugh, as simple as
cables are, I actually had one go bad. Cables are cheap, and if youydon't
already own several, one of your friends probably does. Changing cables is
a cheap test. Do it.
As for salvaging files from a USB drive, most are plain IDE drives with a
USB interface added. In fact, you can buy a USB enclosure without a drive
at many PC stores and make your own USB drive by adding any normal IDE hard
drive. If the problem is the USB interface within the external drive, then
there is a good chance that the IDE drive could be placed in a different
enclosure or attached directly to an IDE cable on any modern (decktop) PC.
The drive will also need a power cable, but those are pretty standard on
most PCs.
But, if the problem is the IDE interface, that is more difficult, since that
is part of the thing we typically call a hard drive. Still, there are
professional services (not cheap) that will remove the magnetic platter from
one hard drive and read them in another. But, if the platters are damaged,
then the odds of recovering data is not good. Most professional services
will not charge much (if anything), unless they can not recover data. Try
searching Google with "hard drive recovery service" to get some idea of the
possibilities.
Good luck.