This worked for me anyway. The mandrake 8(.x) install is as easy as windows IMHO so your biggest decision is probably how you are going to partition your HD.
1. Install XP first (NTFS will work)
2. Install Mandrake, the Lilo (or grub) setup will detect your NT partitions as such.
3. party on dude.
But as KenCleanAirSystem said this depends on whether or not you want to use NTloader or Lilo. I've never tried to use the NTloader to boot linux but I think I'll give it a try, sounds like fun. Good luck to you.