1. Press the <ON> button to turn your calculator on (duh).
2. Type in SYSEVAL 260387
3. Hit Enter.
This will run a crappy little game called Dynablaster. Press the Directional Keys to move, F6 (top right button) to lay 'bombs' and <DEL> to quit.
This game is a bit more fun, I think.
1. Press the <ON> button to turn on your calculator.
2. Type in SYSEVAL 260385
3. Hit enter.
This will run 'Tetris'. Use the keys <4>, <8>, <6> and <2> as directional keys and <5> to rotate the peices. Like the other game <DEL> quits the game.
So next time some one says, hey can you send me some games you can say "YOU'VE GOT YOUR OWN"
(THESE ONLY WORK ON THE HP 39G AND HP 40G)