Unlock Original Prince of Persia:

To find this goodie, you'll need to start from the Above the Baths save, once you have your new sword. Go down the stairwell that leads to a large carvernous area. After you make it through this area, you'll end up in a small room with Farah. There's a lever and gear in the center of the room. Turn it cockwise until it clicks twice. Both doors in the room are now closed, but you have also opened a secret door that you cannot see. Go to the wall directly opposite the entrance. Swing until you find a spot on the wall where your sword doesn't spark. Strike this area a few times to reveal a hidden room. Enter to unlock the game, which is now available from the main menu.

Thanks to Quake2282