Don't know if it works, just stumbled across it.

To launch the ball before the start of the game:

Start Pinball.
Press the F2 button repeatedly 3 times.
After doing so, the ball should fall onto the table before the music ends.

To receive the beginner bonus:

To get the “skill shot” bonus points, launch the ball with barely any force, so that it falls back towards the launcher. It should then go into the play area, and award you 15,000 points.

To drag the ball around with your mouse, wracking up points like no tomorrow:

Open Pinball from Start > All Programs > Games > Pinball.
Type “hidden test” (without the quotes)
Click and drag your mouse around on the pinball table, the ball follows your mouse.

To get one extra ball:
Type “1max” (without the quotes)

To get unlimited balls:
Type “bmax” (without the quotes)

To activate the gravity well:
Type “gmax” (without the quotes)

To promote your rank:
Type “rmax” (without the quotes)

To instantly score 1,000,000 points:
Press Shift + H.

Since I have no social life, I decided to try this out, and it does, in fact work.
Nice one HitSquad, I wasted about twenty minutes of my life getting one billion..

I tried typing them in as I was playing the game. Nothing happened... is there a cheat code box I have to activate?

Just click on New Game and then type it (before you launch the ball)
After this, continue playing as normal, well..as normal as you can play while cheating
Charles