Mine was overheating and the diagnostic called for replacing the video card fan. Instead, I disassembled and thoroughly cleaned it.
I very carefully blew out the cooling fins and fan blades. Since I waited so long, I had to carefully brush of stubborn dust coatings and blow some more.
ALWAYS wear a static strap and use a static mat while the computer is disassembled!
NEVER use a vacuum cleaner. They build up a huge static charge that can easily kill your CPU and other integrated circuits.
If you used canned air, be sure to allow time for your system to completely cool off and never shoot close up, directly on any chips. The liquid form of this "air" can shock the silicon crystal in your circuits and make it crack (die).
Tagged: , pentaxk20d , computer , dell , inspironE1705 , disassembled