1. A computer simulation would probably make more sense than what we see going on around us. For example, what computer simulation is likely to come up with something like "Hunting for Bambi" (see the link below)? The real world just seems too...wierd (or stupid) to be a simulation.

2. What computer can run forever without requiring a reboot? Could you imagine the havoc of a global BSOD (Blue Screen of Death) on a worldwide simulation? It'd have to be a monstrous real-time system, too. It wouldn't be a very effective simulation if hourglass icons kept popping up all the time. At the very least, it proves Microsoft didn't write the code...