My computer shuts down by itself after lagging and slowing down

Let me clarify that it tends not to restart every time it automatically shuts down. In fact, I have to wait for some time before being able to successfully turn on/boot up the computer again. If I try to turn on the computer immediately, it fails to boot. What do you think about such situation? I'm using a desktop.

Over heating is unusual in desktop computers.  Remove all connections, turn it on its side.  Hold the ON button in for 5 seconds.  Open it up check for dust.  Have a can of compressed air handy and blow all the dust out.  You may be surprised.

If you were to bring me your computer:

1. I would probably replace the hard drive and install Windows 7 on it.  Not that it is that likely your hard drive is the problem, but life expectancy is not a lot longer and why put all the work of a re-install in on a soon to fail drive.  Replacements can be had for about $50 or so.  Consider a 7200 rpm one to be the better option.
2. I would take a close look at the fans.  If any are stopped or obviously turning slowly, I would replace them.  Case fans are relatively cheap.
3. Pay particular attention to the video board (assuming you have one installed).  If it has a fan on it (and most do), it is likely that fan has either stopped working or is slowed way down.  Very hard to find a replacement fan for these.  Replace the video board entirely.
4. If the problem persisted after all this, I would probably replace the power supply.  Power supplies are not that expensive (usually well under $100), and sometimes fail in a manner that is difficult to detect.
5. Another consideration is the heat transfer paste that is between the cooling system that is mounted on top of the processor chip and the chip itself.  That paste can become hard and is sometimes not applied correctly.  You can buy a tiny tube of it for about $ 10.  Remove the cooling system -- usually 4 screws and a plug -- then very, very carefully using a cotton que tip remove the paste with rubbing alcohol until both surfaces are perfectly clean.  Then apply very small amounts to near the corners and press together by hand.  Remove and check coverage.  If more is needed add it sparingly where there are bare spots.  Then re-secure the assembly.

It may be an overheating problem caused through duct and dirt and that is normally the main reason for your problem.

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If it was a Hardware problem, it would tend not to restart.

Having said that, it is possible to have a hairline crack in the Motherboard, etc, which only becomes obvious once it heats up

Check the vents for dust, hair, etc and do not use a Laptop when it is resting on material surfaces: bedspreads, blankets, etc.

If the problem persists, as it is a Laptop, take it to a local and reliable Computer Repair Shop and get them to open it up and clean the dust from inside it..

Here is an interesting discussion about the varied reasons for your problem:

http://pc-trickandsolution.blogspot.com.au/2011/07/fix-laptop-overheating-shutdown-problem.html

N.B> However 9 out of 10 cases of overheating are caused by an airflow blockage.

_______________________________________________________

Review safe operating temperatures:

"What should be the temperature of my computer processor?"

http://www.computerhope.com/issues/ch000687.htm

Cheers.

1: Probably as good as any.

2: See> https://www.computerhope.com/issues/ch000687.htm

3: Most likely dust. It doesn't matter what programs are running. It's simple enough to check.

Let me clarify that it tends not to restart every time it automatically shuts down. In fact, I have to wait for some time before being able to successfully turn on/boot up the computer again. If I try to turn on the computer immediately, it fails to boot. What do you think about such situation? I'm using a desktop.

All of that fits perfectly with it overheating. You can't restart it until it cools down.

• Buy some "Air in a Can" from just about any store that sells computers.
• Take the tower outside.
• Remove the side panel.
• Blow out the dust.