I have a mac book pro with 160 Gig internal hard drive. I want to use windows vista or xp on an external hard drive, i already have it installed on the external hard drive already by taking it apart and hooking it up to my friends comp. I put rEFIt and linux on my internal drive already to see if i could boot using grub, but it doesn't show up on the grub list, and i was wondering how i can either boot straight from external or how i can launch from grub.