Do the antiviruses work on previous versions of windows?

As the title describes, i was wondering if the beta antivirus suites, suggested by microsoft, would work on any previous installations of Windows. It is just because one of my friends antivirus, Norton 360 to be exact, has run out, and thought what about it, using the beta versions. I found kaspersky worked and detected best on windows 7, as it found the worst trojans (but only compared it to N360 beta though.
Anyway back to the question would it work on previous windows operating systems, preferably Windows XP, or Windows vista.

Only way to find out is try it, though I say dump norton macaffe and get AVG free edition

There are some exceptions, but in most cases I'd say no. Especially if you are looking to use a 64bit Anti-virus program on a 32bit OS system, that won't work.