PC constantly blocks

My PC constantly blocks when:
1. I play games
2. If I open some web page and I click on some other link before corrent page loads 100%, it blocks
3. When I listen to music ... sometimes, everythuing is ok, but sometimes (mostly when I do something else on PC) it blocks!
4. My Avast did not managed to complete full scan in last month, because PC always blocks ...
5. Hour ago, I was chating with 2 of my friends on msn, and PC blocked.
6. This is all relative. Sometimes, it blocks 100 times a day, sometimes 1-2 times.
And when it blocks, only thin I can do is hold turn ON/OFF button and turn it off. Restart button doesnt work, CRTL+ALD+DEL doesnt work ...

 

The first thing i would do in your place is to open your PC case and check if everything is properly connected, the fans are working fine etc.

The second thing - update all the drivers (videocard, soud, network etc.)

Then i would run a malware scan (check the Malware Removal section of this forum, especially FAQ for more info)

good luck

 

I did malware check (via hijack this and combofix logs) at one of sites in my country. They told me that malware probably is not the reason for this behavior. I'll try first an second thing that you told me ...

 

From my experience, broken RAM relatively often can be a reason of misbehaviour. Try to leave only one RAM module for some time to see how it would work, then replace it with another etc.