A multi-platform regression testing machine

I’m considering implementing a multi-platform regression testing box. This would be used to run regression tests on each of the platforms. My first consideration was install each OS on a different partition/HDD, then boot into each OS for each test. Then I considerered something like VMWare, or Xen.

The pros/cons I thought of were:

	Pro	Con
Multi Boot	Each OS will have direct access to the hardware	Via code, can I get the next OS to boot automagically?
VMWare/Xen	One BIG HDD might do it all No need to boot into the next OS	The hardware needs to be shared (i.e. the tape drive) Is each regression platform supported?

Comments? Suggestions?