I have neglected this problem for a long time now, it has come to a point where the problems are just too big to ignore.

A few months ago, my computer did not boot properly. Instead, it boots off and on and after a period of time, it finally starts and I can use my computer without problem. I only had to press the on/off button once. That 'period of time' has gone on to be longer, from seconds to nearly one minute now.

This week, things has gone much worse. Now, I have to press the on/off button more than one time. Also, when I want to turn off my computer, it 'updates' and than the computer reboots all by himself (not even finished with updating!). I basically have to turn it off twice Today, I've finally reached the boiling point when my computer has reboot 3 times today, automatically. I did not do anything in order for him to reboot.

I have absolutely no idea what to do, can anybody help me?

Specs:
Intel PentiumD 2.8 GHz
3 GB RAM (1x1, 1x2) DDR-2 RAM 667 MHz
ATI Radeon HD 4350

It sounds like you are getting repeated BSOD's, if you see a blue screen with white writing on it just before it shuts down then follow this guide to post you minidump files for analysis.

Please state if you do not see the blue screen then we can run some other tests.

I have no BSOD before it reboots.

I did a System Repair which didnt help, then a Startup Repair and I've turned off the option that it automatically restarts by system failures.

It doesn't reboot automatically anymore (well, for atleast 1+ hour) but I'm still worried and curious about the problems and the cause.

Thanks for helping, I appreciate it ^^

Have you looked under C:Windows\minidumps to see if it has saved any .dmp files?

In the same box where you set it to not automatically restart check these sttings.

You can leave "Automatically Restart" unchecked if you wish.

Do you get a message saying it has recovered from a serious error when it reboots?

There are no files whatsoever in the minidump file. I just followed the instructions in the quote.

It does not give me any kind of error, but I do get the screen where it says the PC wasn't turned off properly and gives me the option to use Safe Mode.

Ok, this brings to mind two other options for the cause, overheating or a faulty power supply.

Download this to monitor your temperatures and report back what they are with nothing running and what they go up to if you try and play a video.

http://www.alcpu.com/CoreTemp/

Is this a laptop or desktop PC?

It's a 4.5-year old Desktop PC. I have tried to plea for a new one but this one has to live for 2 more years.

The Intel Processor is not supported by CoreTemp, so that program didn't work Are there alternatives?

Btw, the PC just restarted twice, even after I turned off the automatic restart option, so I really think it is a hardware related problem now.

Give this one a try. http://www.intel.com/design/motherbd/active.htm

If you know anyone with a similar PC that has the same size or bigger power supply it would be worth your while to swap the PSU's to test your system.

I have no Intel motherboard, so that one didn't work either. I should've said my motherboard was Acer E415SM. However I do have some numbers using another software, you might find something in this attachment.

The PC has been cleaned off from dust.

If the readout is accurate, which sometimes is not the case with voltages, your -5V and -12V rails are both a long way off.

What is the name of the temperature software, I need to figure out exactly what the temps are from. Some are obvious for the GPU and hard drives but the ones for the CPU show three rows of figures, the first two are higher than normal if the PC was idling but the last row showing 80ºC is a lot higher than it should be.

Give me the link for the software so I can look at the details to learn what the read out represents.

Meanwhile I would consider testing all the outputs from your PSU to make sure there is not a fault on the -5V and -12V rails. You will need a volt meter for this that can read DC voltage. If your not comfortable with doing this I would take it to a computer repairer to test it.