Computer restarts on its own - over and over

This started about two weeks ago, and it is getting worse. Every so often, when it would go through the last part of the shutdown, instead of turning off it would just restart. Little by little it has gotten more frequent until now, the only way I can stop it is to turn the power switch off on the back - this is a desktop. If I just push the power button on the front it goes off then right back on. If it follows the normal shutdown, when I click on the shutdown icon, when it finally gets to the point of shutting down, after saving my settings, the power button clicks off, then right back on, then off then right back on etc. It my cycle that way for 5 or 6 times or more and finally goes ahead and boots up even though I told it to shut down. Is it the front power button or a software issue?

 

My Computer->Properties->Advanced->Start and restore->Automatically reboot (uncheck).
Now try to shut down to see BSOD.
Good Luck!!!!

 

Try Goran.P advise first.
Have you make any changes in your BIOS lately?
Do you have an USB keyboard and or mouse installed?
I had the same problem on one of my systems and the problem was I changed a setting to start the PC by USB input in the BIOS. Somehow after that change it had the same problem you are experiencing.
My 2 cents.

 

Well, at first it worked. Sure enough, Automatic restart was checked - don't know how it got checked, because I did not check it and it has been working fine up to a couple of weeks ago - I unchecked it, cliked on shutdown, it went through its normal sequences and turned off. But to be sure I tried it again and it went back to what it was doing - power button flashed off then on, then off then on, then off then on and finally rebooted. This time there were some new hard drive clanking noises and the check drive came up - even though it had shut down normally - it completed that OK, then loaded and I clicked on shutdown and it went through it all then restarted. I have tried it several move times, the clanking noise has gone away but the restarts have not - I have to turn it off with the recker switch on the back. I do have a USB mouse and keyboard but I use a KVM swithch so I can use one monitor with both my computers. The other computer - both desktops, both running XP SP2 - does not reboot on shutdown. Where do I go from here?

 

Ok, I am not expert but will try to help you, it seems like it's a program fault, not hardware, once you check mark "automatic restart" under System failure it means there is a power off software error, look for an error under System log, go to Control Panel, Administrative tools, Event viewer and double click on System, look for an error there and try to analyze what they tell you. I know that it was working before but if I was you I will try to isolate that PC, it means his own Monitor, keyboard and mouse, that way you eliminate the KVM switch and or software relate to switch.