According to Crucial, you can only install up to 4GB maximum of PC2-5300 memory in there (
http://www.crucial.com/store/listparts.aspx?model=XPS%20710). 4 modules may cause the electrical signal to become indistinct, and the system may slow down to compensate or crash. 2GB would be the safe amount to run, but you don't need a 64-bit OS to make use of that.