http://www.lgutschow.com/wp-content/uploads/2011/03/Pcislotzoomedout.jpg
Here is a pictor. ;d
There is only one slot it seems, meaning you can only have ONE ram stick at a time. I believe it uses DDR2 and that means you will need to go hunting for an old stick. ;p
DDR3 is the market majority right now, and DDR2 has been phased out for many years, you'll need to check on eBay or possibly upgrade to a better compy. ;x