I took a piece off my computer and I saw two slots and there are two sticks of RAM. I would like to get a 512MB and replace one for a total of 640MB or something. I posted something on another forum and they sent me to Cricuial or something and that site told me that PC-2700 would work but on the two sticks of RAM in my computer it has PC-2100 so i'm a little confused. If I do purchase a stick of RAM where would be the best and cheapest place and how do I install it and get it working right? Thanks for your help.