A while ago, I bought a used Dell Precision M4400. I love this little laptop: 1920x1200 LCD display. Recently, I installed a 512 GB OCZ SSD and the laptop absolutely zooms.
One thing I noticed was it always seemed to run warm. If I watched a youtube clip, the GPU and CPU temperatures would go into 70-85C. I even saw the occasional 90C+ on the core.
Today, I opened it up and blew out a dust clot off the heat sink's fins. Next, I added additional thermal paste - I should have removed the old paste ... but I didn't. :)
At idle, the GPU is currently running at 47C and the CPU at 44C. Watching a youtube video my GPU is at 52 and the CPU at 51.
Without the fan kicking on, it's nice and quiet.
My final test was to watch a youtube video in 1080p/full screen. This finally tipped the temperature up a bit 64 for the GPU and 72 for the CPU. The fan, barely audible as it's not overheating.