Posted 14 October 2009 - 06:06 AM
Nope, you don't need an OS on it.
For decades, now, I have had at least three drives in my systems; one for O/S and programs, one for temp files and archival storage (two partitions), and one for my data. If you set the data drive to be the same letter (I use E:), you can also easilly use TweakUI in XP to set the paths for My Documents (etc) to match those used by Vista.
P.S. Having a dedicated partition for temp files (first partition on a separate physical drive) eliminates all of the seeking needed to create temporary files and gives the system a serious kick in the behind. For your dual boot; though, I'd make a separate partition for each O/S.
Computer dinosaur, servicing PC's since 1976