Windows 7: Laptop restarts after shut down

Well as many other.
Every time i shut down my laptop it reboots again after 5-7 sec.
I've read and tried all (yes all!) of the solution out there. All the way from editing the regedit to flash bios.
Nothing seems to help. Now i'm out of ideas, and my last way out is to try good old XP.



What i did notice is that if i unplug the AC adapter the laptop stays off, but never with AC plugged in.

Bump

Run a few Startup Repairs to see if anything at boot needs repair.

Next try creating a new User Account in Control Panel to see if it behaves the same way.

If not work through these other Troubleshooting Steps for Windows 7 including the hardware tests. If a Repair Install fails I'd shrink C to do a quick test install to another partition to see if it continues which points to hardware as culprit.

Does Hibernate work in the meanwhile?

Thanks for the info. I'll give it a try later today.
The wierd part is that this problem never happened before with Win 7 Home. But after i updated to Win 7 Pro it suddenly appeared. After that i have formated and made 3 clean installs of Windows.

A quick question.
What happens with all my files, drivers and programs if i choose to repair my Windows?

Where did you get the Pro Upgrade? Did you do an Anytime Upgrade from Home Premium which is the way it's intended to Upgrade to a higher version?

Which extra features did you require in Pro? It is the same OS otherwise. Compare Windows 7 Editions - Windows 7 Forums

You should always have your files backed up in case of HD failure. Do that before running Repairs.

You might also consider a reinstall of Home premium if that's all you need, to see if it shuts down correctly. If so you can Anytime Upgrade using the Pro key if you actually need it's few extra expensive features.

Sorry if i'm vague, English is not my native language, so be patience with me
I bought a laptop with Windows 7 Home preinstalled but with no physical CD. So earlier this week i thought for my self that the laptop needed a format since it been acting funny and not performed as it should been. So i just took a bought and unused Windows 7 Pro key and CD that i got from my work to make format and a clean install of Windows.

As soon that i noticed this problem in Pro i went criminal and downloaded Home edition just to see if the probelem still appeared, and yes it did. So i installed Pro again.

All drivers are up to date and i can't find any patches or updates from Dell themself
Thinking about installing Linux just to what happens. If the problems dissapears then it's Windows fault. If not, then it's hardware problems.

Even tried to install a old version of XP "even before SP1" but that gave me a BSOD

It was not illegal to reinstall Home Premium which came with the PC, and which you own for the life of the machine to reinstall however you wish.

However if you have a retail Windows 7 Professional copy with Product Key then it should work as well.

Does the issue occur as soon as the OS has been reinstalled before Updates or any other drivers are installed?

If the repairs don't help you might try wiping the HD first with Diskpart Clean Command before following these same steps to get a perfect Clean Reinstall - Factory OEM Windows 7. This will clean the boot sector which may have some bad code.

Otherwise it looks like you'll need some hardware expertise.

Yes, i've tried everything.
A clean install of Win, a clean install of Windows with all updates, a clean install of Windows with all drivers and a clean install of Windows with all updates and all drivers. All of them gives me the same problem.

I have not tried to repair the disc as you states before since i'm tired of reinstalling Windows. It just takes to long to install all thoose updates and drivers, especially SP1

But i give it a try later on this week just to see what happens.

I've done some more research and ended up with Linux live cd just to see if the same problem occur, and yes it did. So it's not just Windows. And it seems like MANY other laptop users have the same problem.

I found one problem though in the Windows logbook that comes every time i try to shut down the laptop, but it is in Swedish so i have to translate it with my fine tuned English

-Performance power management for processor 0 in group 0 are inactive due to a problem with the built in software. Check with the manufacturer if there are any new updates.

Well, as i said before. I've installed all the drivers that i could find at Dell :/ Any ideas?