My kid's laptop did that. I opened it up and sure enough a small scrap of paper was in the fan area.
I have had an HP Pavillion dv4000 laptop for a while, and the most annoying feature about this laptop is the fan. Every time I unplug this computer from the power supply, it makes this horribly loud buzzing noise. It sounds like a vacuum cleaner, and since I need to study in a library often, it is a huge pain. Does anyone have any solutions to fix this problem? I was looking into a program called RMClock. Does anyone know how it works and what to do?