I built this machine and it's been running well for a year and a few months, but recently it has been having problems:
ASUS P6X58D-E motherboard
Intel Core i7-930
6GB DDR3-1600 RAM
1 TB, 1.5 TB, 250 GB hard drives
Radeon 5870 1GB
Linksys WMP600N wireless card
Windows 7 x64
Since around July I have experienced random freezes. Everything just stops on screen, audio cuts off, USB devices (ex. iPod) think they're disconnected, the keyboard caps lock light won't change, etc. There is no BSOD or anything in the Windows event log upon rebooting that would hint at a problem. Anyway, these freezes started out relatively rare; I think it only happened twice in July. In August they started happening more often, like once or twice a week. Recently they've gotten completely unbearable, and more random-- sometimes I'll go 15 minutes without it locking up, other times two days. It is not dependent on CPU/GPU load-- it often happens while the machine is idle, and has also happened while playing TF2 and Minecraft. I can't do anything with this machine any more if this keeps up.
So, I figured I messed something up when I built it that was coming back to bite me in the ass. Checked BIOS settings-- everything okay. Heard that bad hard drives can sometimes cause lockups so I ran Western Digital's drive diagnostics on all the drives (they're all WD drives) including full surface scans-- nothing is wrong with them. Ran memtest86 to check the RAM, no problems. However, I suspected it was the memory anyway because I had started out running the (DDR3-1600) RAM at DDR3-1066 speed and had only gone back and set it to the "proper" speed after a few months (during last winter). Sometimes after the computer froze, it would fail to boot up at all (the machine would whirr to life for a few seconds, turn off on its own)... but it would boot up okay if I pressed the ASUS specific "MemOK" button that would mess with the RAM timings until it found something that would boot. I suspected that I had damaged the RAM or something and that was making it unstable, so I RMA'd the RAM. I got new sticks back and installed them (and also set them back to DDR3-1066 again because that would stress the parts less and I couldn't tell the difference anyway), and the problems continue, so it isn't bad RAM. Hell, I can even run a stress test like Prime95 or LinX absolutely fine for hours on end... the freezes just happen completely randomly. It's not even Windows specific, so it isn't a driver problem-- happens on my third hard drive's Arch Linux install too.
I'm not sure what else can cause random freezes. Anyone have any ideas as to how I can make this thing stable again... or is it undiagnosable, and it'd be better if I just cobbled together a new computer somehow? (Although I have no idea how I would do that... I'm in college right now so my purchasing options are very limited)