Why is my computer shutting down all the time?

For a while now my computer keeps shutting itself off, sometimes after a few hours sometimes after just mintues usually when i'm trying to do a scan or installing things. I have anti-virus software (mcafee) installed and recentley i had to do a system recovery as everything was so slow, my keyboard wasnt working properley and it was shutting down all the time. Since i did the recovery it is running alot faster and my keyboard is ok now but it still shuts down alot. I've been told it's not the fan because if it was my computer would stay on for hours at a time.

Any suggestions what it could be or what i could do?

Many thanks.

Why is my computer shutting down all the time?spyware removal

One common reason for a ramdom reboots (restarts) is CPU overheating due to a build-up of dirt, dust, pet hair, cig smoke, reefer residue, etc. that is clogging the cooling fan(s) and heat sink. Very common if the computer is a few years old.

However, there are many other reasons.

Why is my computer shutting down all the time?virus protection software

When I had this problem I looked in power options and some stupid spyware programe had set that to shut down every after 20 minutes,but as others say,it could be many different reasons
It may not be your software that's the problem. It could be your hardware. It might be your power box not giving the computer enough power to be powered, Your mother board could be fried, or your computer parts are not fully plugged in.