Are you sure the thermal paste is applied well? Not to thick applied? 75oC is a lot, can you still touch your CPU cooler without "burning" your fingers? If you can; make a pictures of the inside of the case and the side panel... EDIT: crahak, stop posting a few seconds before me , it´s not first time ... EDIT2: So, it sucks the air away from the sink? Normaly it blows on the sink...