PC restarts after shutdown

Windows XP w/ SP3, Sony Laptop VPCEB1GGXBI. Every time I select shutdown from the the 'shutdown' menu, the PC goes thru the shutdown routine and says "Shutting Down..." but always restarts after the shutdown routine is done. If I tap the power button, the same thing happens. If I try the shutdown.exe via command prompt, it restarts. MalwareBytes found nothing, I ran the Tweaking.com All-In-One Repair and it didn't fix the problem, I removed Roxio software and that didn't fix it, I went to My Computer > Properties > Advanced > Startup & Recovery > Settings and unchecked the "Automatic Restart" option and that didn't fix it either. I uninstalled and reinstalled the video driver, audio driver, and chipset driver and none of that fixed the problem. I have checked all the BIOS settings and there's nothing that mentions anything to do with power (it's a really lame and rudimentary BIOS) but I did change a few things just to see what would happen and that didn't fix anything. I read 3 or 4 threads here at MG that mostly deal with Win7 and nothing I found helped. I've done a ton of Googling and nothing has fixed the problem. EVERY time I try to shut down, the PC will ALWAYS restart as if it had just been powered on, Sony VAIO post screen and all that. Holding down the power button for about 10sec shuts it off, but thats the only way to power it off.
:confused :mad

Any help will be appreciated!

Happy Holidays!

 

Don't have any suggestions, but sounds like the power button may be defective. Maybe someone with more extensive laptop experience than I can shed further light...

 

The power button is fine: the PC powers on w/o power problems; if I press it briefly in Windows the PC goes thru the shutdown process but restarts; if I hold the power button down for 8-10sec the PC shuts off (which is normal). If I boot to a remote environment like a PECD or live Linux disc, the PC shuts off normally. I'm 99% sure it's a weird software problem that I can't locate. I'm running sfc /scannow right now and we'll see what that does (if anything)...

 

Restart instead of shut down
http://www.aumha.org/win5/a/shtdwnxp.php
Since this is very old, the solutions are probably no longer applicable.
But disable restart on error and you might be able to see exactly what is causing the problem.

If that does nothing, open task manager and start killing things. Maybe one of those is causing the problem.

 

Are you able to shut down from normally from Safe Mode? If you can, then you know it's not the power button and you can be confident that it IS a running app (in normal windows mode) that is interfering with the shutdown process.

 

Safe Mode has the same results; PC goes thru normal shut down, then restarts as if it had been just powered on. The ONLY way to power off completely is to hold down the power button for 8sec or so.