I've got a multi hard disk setup on my system, one with Vista and one with XP. Only because of personal preference I like to keep things like that separate, to a degree.

Then all I have to do is press F11 to choose which device to boot from, if your board doesn't give you this option however, everytime you want to boot from the other drive you would have to go into bios and select the hard drive.

Good Luck!

Martin