Instructions
Deleting Game Information/Demos
Turn on your PS3 and select the "Game" option from the main menu. Select "Game Data Utility" before continuing to the next step if you wish to delete game information rather than just a demo.
Scroll down the list (either of game data or game demos, depending on which menu you are in) until you locate the entry you wish to delete.
Highlight the entry and press the "Triangle" button on your PS3 controller.
Select the "Information" option.
Select "Delete" and confirm your decision when prompted. This will delete the information or demo off of your PS3's hard drive.