Over the past month or so, I have had my computer spontaneously reboot, while under a mild load. There also seems to be no rhyme nor reason to when it does it. Sometimes I am doing something rather entensive, other times I am just surfing the internet. And also, it doesnt do it regularly, sometimes it will happen two or three times in a day, and sometimes it will go a week without doing it. Any ideas? I have done fairly extensive Spyware and Virus scans in the past two weeks, I have some hard drive fragmentation, but i cant see how that could be causing this. The computer will immediatley start back up with no difficulties when it does this, so I dont THINK it is heat. But i have turned on my monitoring software to keep an eye on that just in case. But does anyone here have any ideas?

What heat monitoring software are you using? Did you try SpeedFan - Access temperature sensor in your computer ?
Also, there's a great resource here for this issue: Random Reboots? Stop....read this first!

I am using ASUS's PCProbe II that came with my mother board.

But I am not think it is heat. It rebooted last night when my CPU (Pentium D 830, 3.0Ghz) temp was at 44C and my MB temp was at 42C. Which from all i read isnt a bad temp.

But I am happy to try any suggestions, lol.

edit: and after reading that article, i am more convinced it is a PSU issue. My monitoring software also monitors voltages...and I am not sure how stable their numbers should be, but they sure seem to jump around alot to me.

well i just ordered a new PSU, I will let yall know whether or not it clears up the issue.

Alright sorry been quiet for so long on this. But I have been trying many things to fix it.

First I disabled the auto reboot in Windows XP. So I am getting a BSOD now. And it says that I am having a Machine Check Exception.

I had no idea what that meant so i started fooling around with things.

On my system I have two hard drives. One running XP64 the other running XP32. I generally use the XP64, so i thought i would try the XP32 for a while, see if the problem was related to XP64. It wasnt, infact the problem was worse on XP32. Which made me think that perhaps it was a problem with the Drive that XP32 is installed on. Since that drive is referenced on occassion from the the XP64 installation. But recently both drives have been throwing the problem with escilatting commonality. Where it used to happen once a week, it is now happening about once an hour. So I really am afraid to use the comp much until the problem is fixed.

I have changed out my 580W power supply with a 700W. But there has been no noticable change. Except that the problem is escilating. Although I am not sure they are linked.

I have run memtest. For a good day, and gotten no fail messages.

My CPU temp never goes over 52C (at full load) and my Motherboard temp never gets over 42C. I have left the side panel off the system at the moment, just to increase airflow just in case.

I also recieved some popping from my sound on XP32, so i moved my sound card to another PCI slot, and it seems to be working fine now.

I have also sent in a help request to Intel, since they say the CPU manufacturer can diagnose what is causing a MCE, but I thought I would post here...basically because i am desperate for some input. Any ideas?