computer turns off by itself?!?

Your motherboard may have a setting that will automatically shut down your computer if the system is overheating.

You would have to check your BIOS settings. This can usually be done right when you turn your computer on, by pressing a certain button (Delete, F1, F2, etc). Usually the screen will tell you which button to press, but it must be done quickly before Windows loads.

If you think it's a heating issue, try adding more fans or better fans. Ensure that they are running when the computer turns on. Also, clean out any excess dust that might be stuck around your CPU fan or blocking the holes for your case fans.

Good luck!

The CPU, motherboard and/or power supply is overheating which is why it happens when you're watching videos or running several applications. If it's the CPU or motherboard, the onboard temperature sensors are detecting the problem and shutting down to save the computer. Normally, the computer should beep about the overheat condition but yours may be different. First, while the computer is running, put your hand near the fan at the back of the computer where the power cord plugs into the box. Make sure you feel air flowing. If you don't, then the power supply's fan may be dead. You'll need to replace the power supply (or have a repair person open the power supply to replace its fan). If the power supply is moving air successfully, and you're comfortable opening your computer, open the box and locate all the fans that are inside. There may be one or two mounted to the front, rear or sides of the case. There will also be one on the CPU with a large metal heatsink. Make sure that the one on the CPU is working. If it's not spinning, start playing a movie and it should start going before the whole system turns off. If the fan never turns on, it needs to be replaced. Check the other fans in the case. They may only turn on when the computer is working hard so play some videos and see if they start running. If one of them is dead, you may want to replace it. The most critical fans, though, are the CPU and power supply ones. Now that the computer is open, clean all the fans and vents with compressed air. You can buy cans of compressed air from computer/electronics stores. DO NOT use a vacuum cleaner as it can generate a lot of static electricity as well as suck up little parts out of your computer.

Place your hand on the top of your pc at the back, above where the the Power supply is,if you can feel the heat from the p.supply through the case then it could be the Psu.If you think the heat you can feel is Hot then its the thermal threshold in the psu thats making the pc shutdown to avoid damage.

When u turn on the pc from cold how long it is till the thing powers down??? and does it power down when the pc is idle and your not using it or when you start to play a game or run something..

you should check the psu is blowing hot air out of the back of the pc at the top behind the psu.

your should also remove the side panel and check the fan above the processor is spinning freely and not clogged up with dust and dirt as this will make the fan work harder and cause the bearings to fail.

How old is your computer?

Is it a tower?

Is it used in a dusty location?

Sounds like it needs a serious cleaning, not only inside the tower, but also in the power supply, whic all require dismantling and careful static free cleaning.

If it's more than 6 years old, the heat sink on the proccessor may also need to be removed and re-installed using new heat grease. As the computer gets older, the heat sink grease tends to dry out and stops doing its job correctly, causing the proccessor to over heat.

I know you probably didn't want to hear that, but those are the most likely causes.

However, if you care to scan your computer for viruses, malware and spyware, although I have never heard of a worm that shuts down your computer, here is a web site where you can do it all for free. The virus scan takes awhile depending on the size of your hard drive and your connection speed. I hope your computer can stay awake long enough to use it.

http://www.trendsecure.com/portal/en-US/

Good luck

1) Get an antivirus. I use something called NOD32 and it's worked very well for me so far.

Avoid AVG, it is the worst pile of rubbish going. My friend had it and it managed to bypass alot of bad stuff. Not to be trusted!

2) It sounds like your power supply. If your computer is going to fast for itself, you need to let it keep up.

Also, having a good cooling system is vital. Your processor should have a good fan, check if it's clogged with dust and brush it out gently with a soft brush.

Make sure your case's outlet for the fans air isnt obstructed in any way.

BUT, it could be any part such as your RAM failing at a big task, or your processor failing at doing something it doesnt like.

I'm not sure.. but if you computer is getting to hot it may be the problem.

To keep your computer cool.. do check the fan.

Dust it (with one of those air in a can)

Make sure the room your computer in is well ventilated.

And if your computer is a laptop make sure you don't put it on blankets and stuff like that because it just blocks the fan.

It's probably not a virus... it sounds like a hardware issue and it is overheating. Open it up and blow out all the dust, check connections, etc. Sounds like a fan isn't working.

Right now Avira Anti-Virus is the top rated free anti-virus program if you want to go that route just in case.

It's probably the fan. If the computer says that it turned off because of overheating when you turn it back on, then it's the fan. I had the same problem. After the fan got cleaned, the computer hasn't turned off.

It sounds like your PC is over heating. Make sure that your PC has adequate cooling, and make sure that it isn't in an enclosed space, like a desk's computer tower with the door closed. I recommend that you first move your PC to a more open spot, clean your fans, and then install more fans if necessary. Oh, and don't screw around in your BIOS!

Also check your USB ports. When visiting my mums I was using a USB external modem and my PC started randomly rebooting itself and sometimes I couldn't get it to boot up either. After pulling things out putting it all back in agan and playing with this plug or that it turned out that the port I had my modem in was the problem because as soon as I moved my modem to a different port it stopped acting up.