Over the last 3 days my PC keeps randomly locking up and won't always reboot properly unless the power is removed from the PC for a minute or so. At first I thought it was the memory but 4 hours in memtest reveals no errors. It mainly occurs whilst playing a game but it has also happened whilst browsing the net and even once whilst I was in the BIOS. Any ideas as to what it could be as it's getting on my nerves now. Spec: Athlon 64 3700 (s754) Asrock K8NF4G-SATA2 1Gb (2x 512mb) Geil Value PC3200 Sappire X1800XT Antec 500W PSU 2x Samsung HDD's None of it is overclocked.