Not only an you turn the included firewall off, but it notices most 3rd party firewalls and plays nice with them (the new "Security Center" will detect most anti-virus and firewall apps and make sure they are running and whatnot). As far as the 64 bit stuff is concerned, the data execution protection feature is probably what's being triggered here...are you sure the machine is virus free? Data execution prevention is a hardware feature that tries to prevent (or at least mitigate) buffer overruns (which are a class of bug that is arguably the biggest source of security flaws in computing...old timers will remember that the first big Internet worm was a buffer overrun problem in a Unix mail program and it brought the entire Internet down).