Compaqs are pretty picky on what memory modules they work with. Unless you want to go for Compaq branded (quaranteed to work) modules, pick up Kingmax SODIMM module. Those are not expensive, and they should work OK. I have installed Kingmax to 4 similar (Athlon/Duron based, KN133) machines. I had problems w Apacer and Crucial modules. Dont know which other brands would work...