Thanks for the help, but it seems now that all problems are gone. I don't know what happened, maybe cause i updated all possible drivers with the latest.
Now everything runs perfectly and i'm not regretting the 29 bucks anymore.
I was about the buy Start8, cause of the start button, but i actually get used to the new start menu.
In fact i find easier to click in the low left corner to access the start menu. It's fast, it pops out instantly and you don't need to look where you click.
I'm enjoying now windows 8