I'm not quite a typical user, but here's my setup on my desktop /development machine:
I've got 3 hard drives installed and 1 DVD/CDRW combo drive. On one drive, I've got XP installed, On the 2nd, I've got Win98 installed (So I can develop DOS applications), On the 3rd drive, I've got Linux (Knoppix) installed. In my BIOS, I've got it set to boot from the Linux drive.
When it boots, Linux brings up a boot menu, asking which drive to boot from, Linux, XP or 98.
I think you should be able to partition a single drive to do something simular.
-PMF