Hi,
I just decided to download The Witcher 2 EE on Steam yesterday and when I went into the game, after I tried creating new game it's just out to desktop, and the game disappeared shortly after that. I tried to validate the game 2 times but nothing worked. What should I do?

I would suggest that you go to the Steam forums and ask there, since you got the game from Steam.

Did you try to get your backup copy on gog and use that instead? Maybe the steam client itself is causing the problem and the drm free version on gog will work.