yes, it's no problem really. there are lots of questions about dualbooting with xp on here, have a search....
generally tho, mandrake will probably do a slightly better job than redhat with dualboots and stuff. all i'd suggest, as i ususally do, is that you actually DO install a boot loader, but actually swap around the two drives, with xp on the second drive. This means that the boot loader would not be on the windows drive, and so would leave that drive totaly alone.