Having lined the exposed inner surfaces of my Chieftec case with bitumen panels and foam-backed bitumen panels (the stuff designed to damp speaker cabinets - sorry, no pics) I did wonder whether it raises case temperature?

I ask because my HD (Maxtor D740X) has started to whine and it made me think...

The only case cooling at the moment is from the Zalman Flower Cooler and the power supply. All vents are opened and the exhaust fan was removed to clear the grill for better airflow. I don't have a temperature sensor, but to touch, the foam 'feels warm', so I think it may do a good insulating job. Anyone got any concrete evidence to back this up, and am I taking a risk?! My CPU idles at 50-55C, mobo at 30-35C.

The distance between the CPU fan and the inside lining would be the most important consideration. The fan needs a certain volume to work effectively, but as long as the air has no impediments inside your case you should be fine.

There's loads of room for the fan - the foam is only 1cm thick.

Sounds like it should be OK then, thanks.