I have a late-2006 MacBook (2.0 GHz Core 2 Duo Merom) that has been serviced several times. Its had the fan replaced twice: once in the summer of 2007 because it completely failed, and once in the summer of 2009 because it had been making clicking noises. The logic board was replaced last November because of some minor issues with the headphone jack, along with the LCD which had some gray dots starting to appear. Im not sure how long its been doing this, but the fan seems to be running way faster than would be normal. The fan never seems to run below 5000 RPM, and once the CPU warms up, it seems to run continuously at 6200 RPM (the maximum speed). smcFanControl (set to Default fan speed, the minimum) usually reads the temperature as being between 145 and 155 degrees Fahrenheit. I took the keyboard off yesterday to clean dust out of the fan, but it didnt seem to do much. Im pretty sure this isnt a software issue, because the fan also seems to run a lot when the MacBook is booted into Windows 7, although Im going to try booting it from the OS disc and an external hard drive just to be sure. Ive tried resetting the SMC, and Im pretty sure I tried resetting the PRAM a while ago. The only remaining thing I can think of is that when the repair tech replaced the logic board, he didnt apply the thermal paste properly (the optical drive was replaced even though it was working when I sent my MacBook in, two hinge screws were overtightened, and the bezel was not installed properly). Are there any other things that could be causing my MacBook to not cool properly? If booting from another copy of the OS doesnt change the fan speeds, Im thinking about taking the heatsink off this weekend and applying some Arctic Silver.