When you turn on your PlayStation 3 for the first time, you are asked to set up a user account for the console. This first user account is deemed the "master account," similar to the administrator account on a PC. If you want to delete your master account at any time (for example, if you want to sell your PS3), you can do so using specialised commands on the PS3's menu.
Turn on your PlayStation 3 and open the "Settings" menu on screen.
Scroll down to and select the option reading "System Settings."
Choose the option reading "Format Utility." Select the listing for the PlayStation 3 hard drive on screen and press "X." This will delete the master user account on your PlayStation 3 game console. This will wipe all data from the hard drive including account settings, game data, save games and any content you have downloaded from the PlayStation Network Store.