Don't assume that because someone has shared a file, it's going to work. Be careful when downloading any .zip or .exe, so many of these are infected. Read through this sticky, it has a lot of advice & info on virus probs
http://www.gnutellaforums.com/showth...threadid=41432

Even if they're not infected, most games won't work because they either are missing components or need a CD to run Some scummy people do deliberately share infected files.