Steam game won't launch

Just bought/downloaded Portal 2 from Steam yesterday for like $7. When I go to launch it a small popup appears saying "preparing to launch." The popup goes away after about 3 second and then nothing happens, no error screen or anything, game just won't launch. I've already reinstalled it and restarted computer, this my first time actually downloading a game rather than having a disc so I'm confused. Help would be much appreciated.

Update DirectX, update your video card drivers as well.

http://www.google.com/

Did that and still won't work but thanks for the help

My boyfriend suggests that you check the cache integrity.

small window appears and says "one file failed to validate and will be reacquired"

I close the window and that's it, it never reacquires anything and game still won't work

I'm taking a rather wild guess, your Steam Client might be fucked. I've had it for 2 years and that's never happened to me.

Uninstall Steam then re-install it through the Steam website. Your games will be kept safe, so I woudn't worry. If that doesn't solve your problem then, after installing the new Steam Client, try Verifying Integrity of the Game Cache again. Installing a new client might fix that weird problem.

If none of that works, are you sure Portal 2 is even compatible with your laptop/pc? If yes, I'm out of ideas. If no, there you go.

You can try right clicking portal 2, properties and verifying integrity under local files

So simple, why the hell didn't I try that, anyway it worked and I thank very much. +rep for you my good sir