Ive got a computer I think might be underpowered at full load. Windows 7 will lock up, but if you wait a min or two and it will start responding again, but then it will just lock back up. It took me 10 mins today to get the task manager open to try to close stuff but its so unusable pretty much your only option to hold the power button and shut it off. Once Windows is back up there is nothing in the event log besides the unexpected shutdown. The PC is an E6400 on an Intel branded 965 board with 4x1GB DDR2 RAM, an 8800GT and 4 hard drives in a 2 raid arrays. This is the PSU it has http://www.newegg.com/product/product.aspx?item=N82E16817103937 Im pretty sure Im at the limit for that PSU so thats why Im thinking it might be the culprit. Normally it runs GPU F@H and today I was rendering files in CS3 when it started locking up.