Q: My PC Keeps Restarting on its Own
There are several things that could cause this problem.
1. First of all make sure you are getting good clean power. If you have not done so already, get yourself a surge protector. Better yet, get a UPS (Uninterruptible Power Supply). Fluctuations in power, like brown outs (drops in power), system surges (spikes), flickering power could cause your system to freeze up or reset. Dirty power can be the source to all sorts of computer problems. The system clock needs a smooth steady source of power to operate reliably.
2. Make sure that your computer is operating in a static free environment. Ideally your chair and feet should rest on static mats. It also healthy to run a humidifier in the Winter. In extreme environments I also recommend a discharge mat for your hands. During the Winter months up North it extremely important that you discharge yourself on a static mats before you touch your computer. Pray you did not damaged the unit from repeated Ten years ago, the Purchasing Director for Snap-On Tools once flew me up to their corporate offices in KENOSHA, Wisconsin in the middle of Winter with the temperature at 17 below, to face off on what turned out to be a static problem. The employees at that time were all equipped with metal desks. They were shocking their desktops without even realizing it. I should also note that it is possible for static shocks to ride in on your network or dial-up connection, which makes it important that your UPS or Surge Protector include a static shield for these lines.
3. Yes, a problem with the hard drive could cause this problem, but it is more likely a memory problem. Typically, if your hard drive is having problems it will cause the system to freeze. Have you recently upgraded the memory on your unit? Please note that all memory is not equal! What is the FSB (Front Side Bus) speed of your system? Don't assume that faster memory will work in your clunker. I have seen mismatched memory cause systems to blue screen more times than I can count. I do not recommend mixing memory of different speeds because these are the fastest components in the computers and timing is very critical to smooth operation. Try removing the memory or replacing it to see if the problem goes away. Virtual memory is stored on the hard drive and the system need to write out information periodically while the system is in use. One of our systems has a hard drive that makes a slight wheezing noise, which you can hear with every move of the mouse.
4. It will be much easier to identify the problem, if you have the system report the information. Right click on my computer then select "Properties". Choose the tab labeled "Advanced". Then click on the Button labeled "Startup and Recover". Make sure "Automatically Reboot" is not checked. Please note that it is also possible for a virus or Trojan to cause your system to reboot. Hopefully you eliminated this possibility by rebuilding your system from scratch and protecting it with a scanner that has "Auto Protect" turned on. Hope this helps you identify and fix your problem.