I can understand the basic priciple but I will be honest and say that is going a little over my head.
Just download the zip file from the website i provided... when the download is done right click the file and choose extract all then extract then open the cupz.exe file(its the one that looks like a memory chip) then accept the windows alert that the UAC(Vista user account control) then in a couple seconds the program will start, then click the SPD tab... walla... then you will know what size memory is currently in the machine... ;)