Just wanted to mention that I service HP Desktops for my employer and we had a rash of them with thermal compound failures causing them you sould like an airplane ready for lift off. Ours are socket 478 Pentium 4 systems. The thermal compound becomes chalky and fails to transfer the heat to the 1lb block of copper heatsink. After removing the heatsink and taking q-tips to carefully wipe off the failed compound and have 2 clean surfaces the CPU top and the heatsink surface, I added Artic Silver Thermaltake to the CPU and fastened down the heatsink and had a 60 ->65 degree C drop to 35-> 40 degree C.
The Pentium 4's naturally run hot anyways, and the problem we had prior to fixing this was that they were too loud for the offices sounding like jet engines, and they were thermalclocking down to protect themselves from CPU meltdown, which was causing the systems to become NOISEY and SLOWER.
Check your thermal compound to make sure it is not dried up, and have arctic silver or another higher end thermal compound to apply new to the surface after cleaning the old away with q-tips carefully.
***Also FYI: We also had a rash of these also have power capacitors near the heatsink that were swolen and leaking electrolyte out of their tops in which 5 of 20 systems had to become decommissioned due to risk of smoke show or fire. I contacted HP and India Support were oblivious to this issue.