When i'm playing crysis 2 on multi or single player, it minimizes and after 1 or 2 seconds come back to normal. ( screen is making black for few secs ) what is wrong? i have good pc, good graphic. Someone can help me ?

Sorry for my english.

Hard to tell... Sounds like some other software (antivirus or other background task) is interfering. Close any suspicious application. You could also create a different Windows user account with minimal background tasks.