Maybe a vacuum cleaner would help?
I reckon its Vista taking its last dying breath.
I eventually got around to opening up my HTPC and vacuuming inside (first time since purchasing it in 2008 ). There was dust present, but not in excessive amounts. However, only the outlet side of the box-like CPU heatsink was visible. The inlet side was obstructed by the fan, and the other three sides were covered by a non-removable plastic shroud (to direct the airflow, I guess).I do make a point of vacuuming my machines every few months,
After vacillating, I decided to break the thermal link between the CPU and the heatsink, and remove the heatsink completely in order to access the inlet side. This was definitely worth doing, as approximately 25% of the inlet fins were obstructed with dust. A good vacuuming fixed that.
Refixing the heatsink was more problematic than it should have been, as it seemed slightly misaligned, and required some force to position the fixing bolts so that they would engage. Before refixing, I cleaned the CPU and heatsink and used fresh thermal paste.
Prior to this, I had used "Open Hardware Monitor" to monitor the CPU temperatures. They were typically in the mid thirties Celsius, but accompanied by the noisy fans occasionally. After the cleaning, the temperatures are still in the mid thirties, but there have been no noisy fans in the two weeks since cleaning. Success!
-- from CyberSimian in the UK