Windows 7: Borderland + Window'd mode = Problem

Hi chaps.
Was playing Borderland today on my Win 7 rig and i accidently pressed something to cause the game to into window'd mode.
ive closed the program, reset the comp and even alt+tab in and out and its still window'd.
Im lost on what to do as i was went from XP to 7 and i have to relearn alot of new features.
Heres a picture of what i mean.
thanks in advance

Worked it out, thanks anyway people.
I didnt realise alt+ctrl+enter toggles between window'ed and full screen.

Did you check the in-game settings. I don't have the game yet but i'm quite sure that's where your problem lies. I've seen this issue a lot in Crysis Warhead and the culprit is always the check box for full screen being unchecked.