Forum:How do I restore game display defaults?

OK, I quit Borderlands by going to windowed mode (trying to get a Backpack SDU). Now when I start up the game it opens in windowed mode, and even when I click the full screen tab it doesn't go to full screen the way it used to - I can still see the Windows Taskbar at the bottom of the screen, and the program bar at the top of the screen. Before the game filled the entire screen, no taskbars were visible.

Worse still, for some reason the mouse sensitivity is completely screwed up, and it's super sensitive, which makes aiming damn near impossible.

How do I reset everything to the way it was when I installed the game? I can't play the game like this.

This is on PC, Windows 7.