Computersight -

There are many reasons why your computer shuts off automatically. 

The most common being your computer is probably over heating. All you got to do is move your computer some place where air can reach the fans of your computer. If that doesn’t work then your going to have to clean out the inside of your computer. You can do this by yourself, but consulting a professional is a safer way for you and your computer. If your going to do it your self then follow these steps.

• You first need to open your desk top. Your going to need a screw driver. Find the side of the desktop with small holes, this is the screen. This is also the side that needs to be opened. Turn to the back of the desktop and find the screw that is holding the “screen” on the side of the desktop. After unscrewing the screw, pull out the “screen”. You will find the motherboard and all if these wires. DO NOT TOUCH ANYTHING. Even if there is a wire that’s unhooked, don’t touch it it was like that when you got the computer.
• Your going to see 2 fans. One is for the motherboard and another for the desktop itself. The most important one is the fan for the motherboard. Get something thin like tweezers and pull out the dust. Pull out as much dust as you can. Then move on to the desktop fan. Clean it out with a dry napkin and your done.
• On the floor of the desktop there is bound to be dust laying around there. Clean that off with a dry napkin.
• If there is dust on the wires, LEAVE THAT ALONE. Don’t touch the wires, if there is a lot of dust on the wires, consult a professional before starting to clean the wires.

If this doesn’t work then go to start>run> and type in “msconfig” with out the quotations. Then go to the start up tab and disable everything except your anti-virus. 

If all that still doesn’t work then there might be a virus, you can run a diagnostic but those are expensive and could cost about $80. But it’s better then buying a $400 new computer.

Hope this helps!