Linux does not detect it? I'm not sure if the following will work then, but hell, worth a shot eh?

Too bad you need the data... I'd just nuke the thing in WinXP and see if I couldn't get it working after a heavy format.
First, try "touch /reconfigure" and restart (Not sure if this works with Linux, but I know it works with Solaris... hey, they're similar. *darts eyes around*)
Have you tried
fdisk -l?
(that's an L, btw)
Do you know what partitions are on the hdd? (for example, if hdd1 is linux, and hdd2 in swap, or whatever?)
Anyways, try fsck on that drive. (I belive the command is just
fsck /dev/hdd)
I ask if you know what partitions are on it, because you may have to do fsck /dev/hdd#. Not sure though, havn't used fsck since I first tried Redhat. ;-_-
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Now let's face it, I'm unhelpful as hell in this topic.

You might want to check around and see if there are any ghosting tools for linux that you can use in WindowsXP. (As usual, Partition Magic comes to mind... how I love that piece of software).
This is one of those times when having an IRC server we could all idle on would be helpful.