Is it possible to network 4 computers that are all running different versions of Windows?

I have been trying to get our home network set up and I'm totally stumped as to why it's not working. We have 2 desktops running Windows 7 and Vista, and 2 laptops running 2 different versions of XP. Is this my problem? If not, I will just continue to bang my head on my desk and see if that magically fixes my problem.