Crossfire In Windows7

Sup guys. Few days ago I installed a Windows 7 on my PC. On XP everything was allright. Now, when i downloaded the game and istalled it, it works but, the window is small, on the top left cornet. I tried to change everything in graphic options in game, doesn't work. Everyone got it on Win7 or just I got it? My PC is AMD Phenom X4 945 and Radeon HD4850, 4GB RAM.