Instructions
Load "Borderlands" to the main menu.
Click "Options," the fourth option down the list.
Click "Audio/Video Settings."
Click the arrow on the bottom of the screen until you see the resolution option.
Click "Resolution" until the appropriate dimensions appear beside it. For example, if your screen is 1440 x 900, click until it says "Resolution 1440 x 900." Press "Esc" to go back and save your changes.