yes it's possible, it's called dual boot (you can have more than 2 os in one system).
you can dual boot different os, like vista and xp and/or ubuntu etc.
you can google on the subject for more info and for pros/cons of dual booting.
I have never done 5 partitions however I have had xp home as a base then with vmware run win2000 pro, xp pro and longhorn (way back in the day) running right off the xp home desktop, I think I have screenshot of that somewhere hold on...
got it, this from like 4 or 6 years ago I don't remember which but what you see is the background (xp home desktop) then on the top of that you see win2000 pro desktop, xp pro desktop and longhorn desktop.