Finally decided to solve this issue and went to the store with the graphic to test on their computer, at first they did the normal benchmark tests and the score/fps were good. I insisted to test with a real game, Battlefield 3 at medium, and they immediately exchanged me a new graphic.
Now I have been playing skryrim at max and works flawless, the only problem is that its damn addictive.
Oh and thanks for the tips guys.