well there are a few requirements for the games to run, mostly to do with specs and directx - if they can play any recent-ish game though it should be ok, there are some files included with GG that should be installed along with the standalone (you'll find them in the _commonredist folder)
the other issues are likely all linked, if antivirus are (silently or not) removing files this will lead to the corrupt result
life\'s one big game
windows vista ultimate
i5 @3.3ghz, 4gb ram, geforce gtx460, directx 11