Borderlands on the PlayStation 3 is a first-person shooter containing role-playing elements including quest taking, experience-based character building and skill specializations. The game supports solo play, two-player co-op split-screen play, and four player online co-op. In the two-player local co-op mode, playing with your PS3 set to high-definition video output forces the split-screen mode to display vertically. There is no in-game solution to alter this setting. In order to change the mode to horizontal, the game must be played with the video settings set to the standard definition output mode. This can be done only through the PS3 settings menu on the system's home screen.
Replace any high-definition cables --- such as HDMI or component cables --- connecting your PS3 to your television with a standard definition S-Video cable.
Adjust the video output setting of your PS3 by first selecting the Video Output Settings option in the Settings menu.
Select the connection type. In this case, Composite/ S-Video. This will cause your PS3 to display images at 480i resolution.
Select television type to be the 4:3 setting. This is the standard television setting and the step that forces Borderlands to display split-screen mode horizontally.
Save the new settings by confirming the changes. Begin playing Borderlands to view the split-screen horizontally.