Before you launch the ball in the very beginning of the game enter the following codes.....

gmax - The gravity well should become enabled.
bmax - You should have and unlimited supply of extra balls.
rmax - You should advance one spot in rank. This can be done repeatedly until you get to the highest rank.
1max - You should get an extra ball when you loose your upcomming ball.
hidden test - Control the ball using your mouse

After starting a new game, type in the code "hidden test" to play in debug mode. Then hit these keys for the desired effect.

R - Promotes you to the next rank up.
H - Gives you a high score of 1,000,000,000, but always puts the score below the top highest legitimate score.
M - Opens a box of the amount of memory currently used by the game.
Y - Changes the title of the game displayed at the top of the window from "3D Pinball for Windows-Space Cadet" to "pinball"
3D Pinball: Space Cadet FAQs & Walk-Throughs.