Why does my TF2 close every time I start it?

I was messing with the screen resolution and I set it to "play in window". My game crashed and now whenever I try to launch it, it goes through the VALVe and Source SDK screen and then closes. I can't get back to the options menu to change the settings...what do I do?

I already uninstalled and reinstalled, but it kept the same settings

I think there is some command you can enter in the game properties that will be applied when launched (console, and other stuff) I'm not sure of the command myself, but I'm almost certain it's out there somewhere (there is one to play in window mode, so I don't see whay not full screen)

It's in the options menu, but I cant get to it because the game closes >.<

it isn't actually in the game, right click on TF2 in Steam's 'My games' tab, select properties, set launch options..., and there try writing fullscreen
that should force the game to launch -fullscreen

Thank you Bobi