Locate the Game Save Data on the Backup Device
Plug the external storage device into one of the USB ports on the PS3 system. Scroll over to the "Game" section of the PS3's XrossMediaBar, highlight the "Save Data Utility" option and press the "X" button. Highlight your removable storage device icon and press the "Triangle" button. Highlight the "Display All" option and press the "X" button to view all of the game saves stored in the backup on the external storage device.
Delete the Game Save Data on the Backup Device
Highlight the game save that you want to delete within the external storage device. Press the "Triangle" button, highlight the "Delete" option and press the "X" button. Highlight the "Yes" option and press the "X" button to confirm that you want to delete the game save data and remove it from the backup.
Locating and Deleting the Game Save Data on the System
Turn on the PS3 system and scroll over to the "Game" section of the XrossMediaBar. Scroll up to the "Save Data Utility" option and press the "X" button to view all of the game saves stored on the PlayStation 3 system's hard drive. Highlight the game save data that you want to delete and press the "Triangle" button. Highlight the "Delete" option, press the "X" button and confirm that you want to delete the data.
Deleting Game Saves Using a Computer
Plug the external storage device into one of the computer's USB ports. Click the "Start" button and select the "Computer" option. Double-click the removable storage device's icon to view its contents. Double-click the "PS3" folder, followed by the "SAVEDATA" folder. Click on the game save data file that you want to delete and drag the file into the "Recycle Bin" on the computer's desktop. Double-click the "Recycle Bin" icon, highlight the game save data file and press the "DELETE" key.