At this moment many people seem to suffer from system compatibility issues, mostly caused by graphics cards not having the right features to run the game.
Stacks TNT mainly uses the graphics card for physics calculations and it needs a beefy one to do so.
Therefore it is very important to first run the tech demo to determine if your system is able to run the game before purchasing! If the tech demo doesn't run then the game will not run.
Sorry for the inconvenience.
Best regards,
Roy