Directx error

Hello, when I start the game, the game screen loads, but it gives an error saying something about DirectX and keeps kicking me out of the game. On the rare occasions when it doesn't kick me out, it says 'Press any key' on the login screen, and when I press a key, it closes the game. The key I press isn't Alt+F4, it's just a regular letter key. I spent so much money on this game, and now I can't play it because of an error. Please help.