Several things may cause such a problem to occur.
If you're using Windows XP, see the following Microsoft Knowledge Base article for more information on possible causes and solutions for such a problem:
http://support.microsoft.com/kb/311806
Additionally, check out the below web page link for more good information regarding Windows Shutdown & Restarting problems:
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A power surge can cause that.
Or a defective power supply.
Yes. That happened to me when my computer broke down and we had to get a new one.
Apparently you can't.
This is how you turn off your computer. To access it, go to START (at the bottom-left hand side of your screen) and click SHUT DOWN. Then,k click SHUT DOWN again.
knock it down and then start again
You need to test the power supply.
Hold the power button until it shuts down and then when it has, wait about five minutes. After that, press the power button to start it back up again.
Probably has to do with how many people are on it at that time. If too many people are on one website it will slow it down. But it also could very well have something to do with your computer. It might help to shut down the computer and then start it back up again.
First, the easiest thing to do is to just restart the computer. If you don't want to, the harder way is the shut it down and start it up again. The only way to change the safe mode is to start it up again in normal.
Check timing belt
on newer models you have to hold down the power button to turn it off, and then press it again to turn it on.Older models you only need to press it to turn it off, and then press it again to turn it on.
My 92 PA had a similar problem. Either the cam or crank sensor can cause this problem. If it is the fault, the error code can be read out from the computer. Mine would fail after the engine warmed up but would start again later.
try replacing the ignition coil. after it hots, it starts breaking down and will not fire again until it cools off