Can't start up TF2

[R.M.T.B.]

Whenever I try it just sends me back to my desktop, I opted into sdktools to make backpack icons and opting out of it doesn't work

[BANG!]

Tried restarting steam and even your computer?

[R.M.T.B.]

[QUOTE=BANG!;41966864]Tried restarting steam and even your computer?[/QUOTE]

How do I do that
(restart steam)

[R.M.T.B.]

Okay! I fixed it! I just had to validate my TF2 files