I have an installation with Windows XP and Fedora Core 2 Test 3 and my Windows option inside grub looks like:
rootnoverify (hd1,0) unhide (hd1,0) hide (hd0,0) hide (hd0,1) makeactive chainloader 1+
what would happen if you unhide (hd0,0) (hd0,1) can you boot into xp ?
do you have an extented partition on hda or 2 primaries ? do you have only 1 primary on hdb for xp ?
-- shrek-m