If you REALLY want a multiple boot machine where the various OS's have no way of interfering with one another, do this:
Install a good, high quality aluminum rack and get yourself as many inner trays as you want OS's.
Then fit each tray with a separate but equal hard drive.
Setup each hard drive with what ever OS you want. Then all you need to do is swap trays and boot.
For ultimate slick switching, you need a full tower so you can have several mobile racks. The you just use the external key switch to turn one on and the others off.
This way you don't worry about software boot glitches . . . life is simple, and hardware is much more reliable than software.
