bigw, go to this site http://www.everest.com and download the program called "everest home edition". After downloading, look to the menu links on the left of the screen. Click on +computer and expand the selections, then click on "overclock". After the overclock screen appears, arror down to SPD memory modules to see the who, what, how, and whys of your current memory in your OS. Also, as you'll see once you get into the site, there is absolutely nothing that you can't find out about your system.
Then, when you get ready to order new upgrade to your ram, go to either http://www.crucial.com or http://www.4allmemory.com,and scan your system with either or both. Both will tell you exactly what and everything you need to know about upgrading memory.