1. Check game options for windowed mode 2. Run in virtual desktop, however the screen looks like that because there is no correct resolution in game 3. Are you sure your system freezes? Can you switch to virtual terminal? - If yes, then your system isn't frozen and you can kill the application - If no, then your GPU && driver probably sucks 4. If your system isn't frozen, you could start the game to seperate X display where it's fullscreen, but you can still switch out of it. Best would be that the game offered windowed mode and different resolutions however.
