If you press enter when the mouse cursor is over the window, the game exists. Because thats how you exit it. To enter the game world, click on the lamp, then motor pool, then the door. Also, there is no need to install the version from the underdogs, just unpack it where you want it and run 2000.

Anyone know how to get the mouse to work in space crusade? Clicking works, but the cursor is stuck in the middle of the screen.