I have Chessmaster 9000 and for the last two hours was looking for option alowing two people to play against eachother on one computer.

How to do this?

Okay...

1. From the Main menu, click on the Gameroom.
2. From the Game menu, select 'New Game'. The 'Set up Game Details' screen will be displayed.
4. Next to both players, you'll see two icons: A human, and a computer. Click on the human icon to make that player a human player; or you can click on the computer icon to make it a computer player.