*sigh* It didn't work 100%. When I play games, everything still flickers a lot and I experience some other problems as well.
Should I downclock graphic card?
(actually, I didn't know till' yesterday, that my card is actually overclocked version already ... -.-)
Now I know, that I won't listen to my father next time, he says "PowerColor or Sapphire, it doesn't make any difference". (actually it was Sapphire card, that was supposed be in my new computer, but ... I actually don't know, why I got PowerColor then. I realized it, when I started to read list of components on the way home from electronic shop. -.- But my father knew about this change for at least a day already. -.-)