Windows 7 System automatically shuts down

First off...laptops weren't designed for this purpose do to the close proximity of the hardware inside laptops which produces large amounts of heat and most laptops just have the bare minimum for cooling. There is no modifying the laptop to add extra cooling. So this will shorten the life expectancy of your laptop not to mention what this will do to the battery leaving it plugged into the power adapter all the time.

You don't give make and model of your laptop so advising on your situation will be hard. I would suggest contacting your laptop vendor and putting in a support ticket explaining your problem and ask them how to advise you.