When your computer takes actions seemingly of its own accord, it can be extremely frustrating. Unanticipated shutdowns can cause you to lose data, interrupt gaming or online sessions and in some cases even cause hardware damage. If your computer shuts down unexpectedly, try to find the source of the problem as soon as possible.

Patching and Installation : If your computer shuts down in the middle of a game or other activity, it could be due to a patch or software update. Windows features the ability to automatically download and install important updates, and some require the system to restart. Windows usually gives you plenty of warning before this occurs, but if you are running a program full-screen, you may not notice the warning. You can switch these updates to manual control to prevent this, but you should regularly check for important patches so you do not leave your system open to hackers or malware.

Heat: Your system may restart unexpectedly due to a temperature spike. Both your CPU and graphics card can become extremely hot during normal use, which is why both components come with heat sinks and fans to dissipate the extra heat. During periods of heavy load, however, components may reach temperatures too high for the cooler to dissipate the extra heat. Your motherboard includes sensors that measure chip temperatures and will automatically shut the system down to prevent damage if heat buildup becomes too severe. Heat overloads may be due to dust buildup in the case, improper overclocking or aging components pushed too far past their normal performance levels.

Power Issues: A sudden, unexpected restart may be due to a problem with your power supply or an external power flicker. If your power supply cannot maintain acceptable current to every component inside your case, it may automatically shut itself down to avoid damaging delicate circuits. Similarly, an interruption in the external power may cause the system to reset itself even if the interruption is too short to cause lights to flicker. Insufficient power may also cause the system to shut down the video display, making it appear as though your computer has turned itself off while still leaving other components running.

Malware: Malware may cause a computer to reset itself frequently. Some malicious programs trap the computer in an endless reset loop or otherwise damage system files so that the operating system crashes repeatedly. In other cases, a type of malware called a zombie program may take control of your system and the hacker behind the program may reset your computer in order to install his own software. You can boot into Safe Mode by holding F8 during the startup procedure or you can use a rescue CD to boot into a clean operating system environment to assess any potential damage and clear out unauthorized programs. http://qwikfix.co.uk/acer-customer-service/