Why would a PC restart itself without having been rebooted?

Answer

1. Check powersupply handling capability, test rails with a multimetre NOT ONBOARD VOLTAGE MONITORING

2. Not enough voltage for overclock

3. Overclocked too far

4. videocard,cpu overheating

5. faulty wiring or possible shorting

6. Check All capacitors around the mosFETs supplying power to the cpu, especially if you have an abit/epox board

Check the heat

There are several possibilities for this. In my experience, the most common reason is overheating. If it generally occurs when you are playing full-screen games or other video intensive applications, that is most likely the problem. If you are comfortable with opening your case, you can make it better by getting some canned air, taking your computer outside, and blowing it out, particularly the CPU fan and graphics card fan. ***DO NOT USE A VACUUM!!*** Vacuuming will cause static electricity and can cause your computer to suffer complete failure. It WILL be messy, and if you blow it out inside, all that dust will just end up back in the case. However, if this happens just randomly, I would suggest checking your drivers to make certain that they are updated. If you are running Windows 2000 or later (2000, XP, 2003, or Vista) you should check your event log right after a restart. The event log is located in the Administrative tools section of Control panel. Check your Application and System logs for any red errors (you may need to page down several times to get past the startup events) That MAY give you an indication of what is going wrong

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