You mean attach the drive to the XP? I think it would have to be formatted Fat32 for the PC to see it.
However, if you're on a network, and you share the PC C drive, you should be able to see the PC from the Mac, and transfer the files over the network.
On my network I can see the Mac from the PC, too, but can't see drives attached to the Mac, even with read/write permissions. Not sure why. But you could go through a folder on the Mac, e.g. the Public folder.
/Mr Lynn