Computer Tuneups
These are things we do at my job to give a computer a 'tune up', and most of the time, it kills those aggrivating lockups and surprise reboots.
If you ever suspect your harddrive or your RAM, you can download diagnostics to test either one. The best free RAM tester we use is DocMem and it can be found here:
http://www.simmtester.com/PAGE/products/doc/docinfo.asp
As for your hard drive, find out the manufacturer of the drive, then download the diagnostic utility for it.
In both cases, they will make boot disks and you will have to test them from that.
The next thing that tends to give computers major headaches aside from viruses is spyware: hidden programs that sneak onto your computer from the internet and has strange and unwanted side effects on your PC. One of the better tools to download and use to remove them is AdAware:
http://www.lavasoftusa.com/support/download/
MSConfig is one of your best friends and is where you can go to see a list of what programs will start up when you start windows. Here is where you can see unwanted programs or unnecessary programs that will bog down your machine and sometimes interfere with operation. Start-Run-msconfig<enter> Once you run MSConfig, go to the startup tab and disable everything except: taskmonitor, systray, anything antivirus related, anything needed for your dialup or internet access.
Now in your case, with the surprising reboots, I have found the causes to be either processor overheating, or failing power supply. Especially when you have problems with spikes, surges, or brownouts, you're going to risk electrical damage, even with a good surge strip. So if everything software wise seems to be fine, and your RAM and HD test fine, then the failure is most likely hardware, and I would recommend first replacing the power supply (hopefully, you'll have a spare handy)
If after all the tune ups and the power supply change you still have the mysterious reboot, then your problem is either a processor overheating or a motherboard circuitry failure. Since you believe its not an overheating problem, then I would eliminate the processor as the culprit, and the last remaining item that would be the problem source would be the motherboard.
Anyway, hope that helps.
