ROM's play pretty well, no matter what kind of PC you have these days. So I'd suggest finding Snes9x or something and downloading some ROM's you want to play (rather easy to find over the internet, but I can't say here else I get into trouble!).

In terms of PC, well I'm not really sure. You could always go to www.download.com and check out their games section, some are just trials but there are free ones in there somewhere (they have sections for each genre).