512 DDR is really all you need to know. I imagine it prolly only uses PC2100 or 2700, but if you get a higher speed it will just clock it down to that speed. The only thing you will be screwed out of in that case is some of the extra dough you spent on the PC3200 (or whatever you get).
EDIT: I believe you can use CPU-Z to tell you. go to http://www.cpuid.org/cpuz.php
and download CPU-Z. I believe it will tell you under the memory tab.