most have it printed on a sticker that attatched, or it might be printed on the MB itself. I assume your computer is Dell, Gateway, ect....you can sometimes find out by just doing an internet search for technical data on the model you have.
I've Googled everything to death, and still couldn't find what I was looking for. The mb has a sticker with a number: MBG5409007.......... and a whole bunch of numbers after that. That is the only thing that looks like a part # although the structure of that number is similar to the serial number of my computer: PTG540X005.........
So I've come to a grinding halt, unless someone knows where I can get this info.