On the credit screen, type "DRAGONBRIDGE". A message should appear to let you know it worked. This will give you infinite lives. During play pause the game and press 'L' to skip levels.
Another cheat is: When the game starts to load hold down the mouse button and the joystick fire button and keep them held down until the game loads. Then when the game starts pause it straight away and type 'MNBVC'. This will give you infinite time and lives, and if you pause the game and press 'L' you will advance a level.