Over the past couple months or so, my PC will randomly lock up while I am using it (playing a game, surfing the internet, etc.). If I shut it down and restart it right away, the PC will sometimes lock up during boot, however if I shut it down and leave it for a few minutes then return the PC will start up again and work fine for a while. I've checked the CPU temperature (Intel Q6600 Quad running at 42C idle), the GPU temperature (NVIDIA 8800GTX running at 55C idle), and they both check out as fine to me. I checked to see if my RAM was maxing out for some reason, and at idle I am only using 41% of it (~2 GB of 4GB). I scanned both of my HDD's and one of them the WD Data Lifeguard tools found bad sectors on (unrecoverable ones at that..or so they say), however if I leave this drive unplugged my computer still randomly locks up. My OS is Windows Vista x64 Home Premium, and I haven't had a problem with it thus far, although sometimes it hogs more memory than I would like. I've tried everything I can think of...I even suspected the PSU at one point, however it is a 700W PSU and shouldn't be anywhere near maxed out when I'm surfing the internet. Any help would be greatly appreciated.