CPU - Intel Core 2 Quad Q6600 Kentsfield 2.4GHz LGA 775 Quad-Core Processor Model BX80562Q6600
MB - EVGA 122-CK-NF67-T1 LGA 775 NVIDIA nForce 680i LT SLI ATX Intel Motherboard
RAM - Crucial 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model NE2KIT12864AL804
HD - Western Digital Caviar SE16 WD3200AAKS 320GB 7200 RPM SATA 3.0Gb/s Hard Drive
GPU - EVGA 640-P2-N821-AR GeForce 8800 GTS 640MB 320-bit GDDR3 PCI Express x16 HDCP Ready SLI Supported Video Card
PS - Rosewill RX750-D-B 750W 80Plus Certified, ATX12V v2.2 & EPS12V v2.91 SLI 8800GTX SLI CrossFire Ready Active PFC PFC Power Supply
Case - Antec Nine Hundred Black Steel ATX Mid Tower Computer Case
At first I thought it was a Vista problem, and I pored over the Event Viewer logs. All it would ever tell me after I rebooted was that there was an unexpected closing of Windows. I rolled back updates, I got the latest video and sound drivers, and that didn't fix the problem. I tried loading the OS in Safe Mode and that didn't fix it. Then I got a couple freezes while rebooting.
The case has 3 big intake fans and two exhaust fans, I got a great big fan and cooler for the CPU, the video card has a large fan, and so on. It never feels very hot, and temps seem normal.
The reason I mention the fans is because of the unpredictable nature of the freezes. Since no one thing causes them, and they vary wildly in frequency, temps was one of the first things I thought of. The computer can boot normally to Windows Vista, and I can browse the Internet, play games, etc. Sometimes it will go hours without a freeze, or it might happen right away. I have to reboot via the reboot button on the case. Once in a while the freeze will occur during the POST startup, before the OS is even loaded.
I got the UltimateBootCD, latest version, plus the even more recent version of Memtewst86+, v2.10. I pulled one stick of RAM and tested it, eight passes, before finally stopping it. No errors. I put the other stick in, and ran Memtest. It went 5 passes with no errors reported, then somewhere in the sixth pass the computer froze up again.
I tried doing CPU stress tests, but those seemed to go fine and I quit after a half hour.
The only thing I can think of is that my wife reported to me a month ago that my APC UPS suddenly started with a loud, high-pitched beeping noise (but steady, not intermittent) and showed red lights on the front. The computer shut off. She is not very specific or helpful about details, but I think there must have been a power fluctuation and it went to battery or overloaded. This UPS is from my older computer which had a 450W power supply. This new one is 750W....with just that and a 21" Samsung LCD monitor hooked up, would that badly overload the UPS? Anyways, the buzzing stopped and the lights went green on the UPS, and she restarted and things worked fine. But since that time, these freezes have become more frequent.
Is it possible that this power surge/drop affected the motherboard somehow? Could the UPS be damaged, delivering inconstant voltage to the power supply and thence the mobo? Is there any way for me to test this without specialized equipment? Is it worthwhile to take it in to Best Buy and pay the Geek Squad guys $70 to check it out, or is that a waste of money? I don't have any spares that I can swap things out with.
I've run out of ideas! Please help!