I was suspecting GPU core to go over 80, which would explain the artifacts appearing on the screen. Apparently, that is not the case.

Colors changing, artifacts and erratic lines appearing with immediate crash point to VGA gone bad.

And those noises you hear would probably be fan(s) out of balance. Possibly dust buildup or damaged blades.

I am pretty sure the sound comes from a fan.The CPU or the Graphic Card one.What is more...earlier i tried logging with one of my characters and i experienced one of the issues i mentioned before.It was the last problem with the flashing lines.I tried to get a screenshot and then i restarted.The screenshot showed my desktop normally without the flashing lines....

I managed to get some photos of my monitor when the problem was in progress Will upload them in 1 min

That only prooves that the problem originates within VGA.

Here one from in-game and the other from a black backround in painting

http://img38.imageshack.us/i/dsc00781f.jpg/
http://img200.imageshack.us/i/dsc00779urv.jpg/

What is VGA? Sorry for beeing a noob.I forgot to mention my monitor btw.It's a LG L1900R

VGA is the Video Graphics Array, mainly to connect your monitor to your GPU and process the data.

How long have you owned the graphics card for?

Since i got my pc.It was 2 years ago if i am right.

If the warrany isn't void, use it.

To change the whole machine u mean?If not are there some spesific parts i could change to solve this problem?I am not sure about the warranty and i can't really afford buying a new pc now.

Well, your graphic card certanly needs replacing. If you bought the whole machine as one package, then you'll need to RMA it in order to replace the broken graphic card. Usually, when you buy whole PC as one package, then you get warranty on the whole package.

If you got the components separately, then the graphic card's warranty is what needs to be valid, and you should RMA only the graphic card.

If the warranty expired in either case, you don't need to change everything. Just your graphic card. 8600s are relatively cheap.. and there are allways 2nd hand cards.

To be certain that it IS graphic card that needs replacing, try it in another PC, or try another graphic card with your PC.