Windows 7 restarts automatically, NO BSOD

[kabinash]

My friends lenovo ideapad (i don't remember the model now) restarts automatically.
It also restarts as soon as i plug in the battery charger. There is no error log created inside windows folder. I turned off the 'Automatic restart on system failure' but, it doesn't work. After that my friend did a fresh install of windows 7 ultimate x86, on the system, but the problem persists. Is it a hardware problem?

 

[gregrocker]

Where did you get Win7 Ultimate? How is it activated?

What is the licensed OS which came on the Lenovo? Look on the COA sticker on bottom of machine.

I would reinstall the licensed OS after wiping the HD of all boot code, following the steps in Clean Reinstall - Factory OEM Windows 7 to get a perfect install. Then you'll know for sure if the problem is hardware or software.