I've got a really irritating problem with my computer, I think it gets overheated every time I play a demanding 3d game, or if I have a lot of things going on at the same time.

The computer freezes and the screen goes black, and the keyboard doesn't respond when this occur. I was hoping that my newly invested extra fans would solve the problem, but I still get these black outs.

I first thought it was the graphic card and bad drivers, so I tried installing windows on my second hard drive. But just the same, so It must be a non-software issue. Anyone that has any solutions or suggestions?

Just a few thoughts:

Have you tried using gkrellm to monitor the temperature of your mainboard?

Were your new fans case fans or CPU fans? It's possible that your CPU fan is dying.

Are you overclocking at all?

Try taking off the side of the case to see if that helps.

Check to make sure your graphics card fan is working.

Make sure the computer has lots of space around it, otherwise it might just be recycling the same hot air.

Just to add to pljvaldez's suggestions:

Blow out any accumulated dust from your PC

Verify that the fans are installed properly - the airflow should all be in one direction, with the front fan pulling air in and the rear fan blowing air out.

Haven't installed gkremllm yet, I'm about to.
The cpu fan works, should I replace it?
2 case fans, for the chassi front and rear
bios is default, no clock.
side is off, but I sometimes try to put it on, because the airflow might get better maybe worse.
graphic card fan is working.
I've tried to move the big cords away from the hardware so I can get more space.
I have vacuumcleaned it.
The airflow was in one direction, but then I change the back so it's blowing in, should I change it back?
Still the same problems, maybe I should add that It doesn't always freeze, sometimes it reboots, sign of being overheated?

gkremllm can't find my temp sensors.

How old is the computer? It could be bad RAM modules or power supply. Start by taking out everything that's non-essential. If you have more than 1 memory chip remove all but one and swap them between tests. Then, one-by-one, add pieces and run tests until you duplicate the problem.

the motherboard with the processor is new, less than one year. But the ram-memory and the power supply are old stuff.

Yes. If both fans are blowing air into the case (or vice versa) you are not getting anywhere near the airflow you'd get if the air is moving in one direction, and carrying the heat *out* of the case. If both fans are blowing in, the only thing that's happening is that the hot air is just swirling around inside the case - what you want is for cool air to be drawn into the case, and hot air to be exhausted from the case

I changed it back just after I wrote that reply, After reasoning in more physically way, but that doesn't matter anymore beacouse the computer is dead now, RIP, I can get the power on but now I only get a black screen and I don't hear anyting from the harddrive, it happen after I removed the ram-memories and put them back. WHAT HAPPEND, what should I do?