Portal 2 crashes on startup

[JAYTEE]

Well, my portal 2 crashes on startup. I think this is due to me using a friends account and downloading portal 2. I mean I used his account to play the game.

So far, as soon as I launch it I cant even get the the menu, just the little slideshow. Anyway I really want to play the game again !

P.S. I've already tried to validate the files and type -autoconfig in the startup section (Both have not worked ! :'c )

[Courier]

Try backing up your game files