Dark Messiah of Might and Magic

Hi, I bought this game During the steam sale, and am enjoying it thus far, however, i seem to be in a spot of bother, after I play the game for about 5 minutes everything starts to get choppy, then REALLY choppy, i'm running a Windows 7 computer, if that has anything to do with it.

I really like this game, but it is becoming difficult to immerse myself and play when everything is stuttering, could someone please assist me? Or point me in the direction of someone who can?

Thank you.
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Lost Karma Counter: 6
PSN: kdread1