I swapped my hda and hdb (basically - put in a new hda and moved the old hda to hdb) and have W2K on hdb.
other = /dev/hdb1
label = NT
table = /dev/hdb
Don't think I had to do anything with Windows and just had to edit Debian's fstab and so on, to tell it where it was. Not sure if that would work with XP or what it would take for Grub. I moved the old hdb to a second computer as hdb with Slack still on it and Slack didn't like the i810 video but a framebuffer edit in lilo.conf fixed that - and neither had a problem with each other. The hdb disk just crashed shortly thereafter, though.
Not sure if that helps, but fwiw. It can be very tricky, though - jumper, cable-select, which installed in what order, etc., etc.