This happens very rarely, but it does. I have a quad core Intel Q6600 with 4 gigs of RAM (2.7 of which is recognized under XP), what happens is that once in a while, after leaving computer on for a long time, the computer freezes and I have to reboot. The redicolus thing is that this does not happen on my shitty Athlon 3000+ laptop... I don't overclock, and I have a huge CPU fan with low CPU temprature... What could be wrong...???