Instructions
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.