I've swapped out the MB , processor, ram and powersupply all at once before. Worked like a charm except Windows would no longer boot. I had to format the HD and reinstall windows after such a drastic change.

My advice is you buy a Motherboard, Processor, and Heatsink together as part of a kit or make sure they are compatible as you order it. Memory is a bit easier to match up to your new MB, so you can shop around for that.

I made the mistake of buying the MB and Processor, but assumed my current Heat sink would fit. I ended up having to buy the heat sink afterwards which left my computer out of commission while I waited on the Heat Sink. I also ended up paying the same price as the heatsink in shipping, because I had contract work being held up for lack of a computer and had to pay the prenium price to get it here ASAP.