Good thing I found this thread! I had ap. the same problem as Aky did. Defcon run quite alright, but CPU usage was always near 50% (given I have Hyper-Threading on, I guess it's the same as 100%). It didn't affect almost anything (could watch a movie, convert smth and play Defcon, like the CPU was absolutely free) but cooler on the CPU (or probably it was one on GPU
) was working like mad. I mean _really_ loud. I suffered from this shit pretty long (was too lazy to search for solutiuon).
Installing 91.47 drivers (I don't even remember which I had before
) solved the problem absolutely: CPU usage is now around 8% and there's almost no noise at all 
Many thanks for Aky for finding a quick solution
EDIT:
lol, I guess I was far too optimistic on this one: it only works fro the main menu, lobby... everywhere besides the game itself... oh well, it's better than nothing
EDIT2:
Upon a more carefull testing I found out that it actually worked. CPU usage maxes out only during some in-game moments with lots of thing going on and it's not an issue really
