Have four of these with identical parts... Antec 4480 Case w/ 380W PSU XFX Nvidia 630i Geforce 7150 Mobo Intel Core 2 Duo E4500 775 CPU 2GB Corsair XMS2 DDR2 800 Memory Lite-On 20X SATA DVDRW Seagate 7200.10 250GB 7200 RPM Windows XP Pro SP2 with Windows Update to SP3 current. Computer boots fine, opens programs fine. After sitting idle for a few minutes and it is frozen. Mouse does not move, no response to Ctrl-Alt-Del. Reboot required to restore. Have tried several things. 1) All cooling fans are working. 2) Swapped memory for a known working 2GB kit of OCZ Reaper DDR2 800. 3) Re-installed Windows XP Pro from scratch. 4) Installed latest drivers for chipset, video, and sound. 5) BIOS is current. All of the computers are running the same software, drivers, etc. One different program, Cloud Desktop Spamfilter. Removed the software, still no difference. I am at my wits end. Help!