Re: 4 year old latititude d600 overheats, freezes; how can i open it up to clean it?
Yes, cooling fans do an excellent job of vacuuming in any dust around and the cooling fins of your heat sink hold on to it for you.
Each model is different, my D800 is just two phillips screws to drop the fan and clean, I can let that go for up to a month.
My similar looking D830 is a several hour job, just to get to the cooling fan and heat sink fins, so I use compressed air once a week to blow through those cooling fins, being careful not to overspeed the fan (short bursts).
Dell has your Service Manual online for View or Download; click "Support" at top of this page and then select Product Support and "Manuals".
This will open a 'pop-up' for you to enter Service Tag (or model) and you can see way to your Service Manual and how to disassemble.