shellroc
You can buy memory, that's certified to work in your 5150/E510, from here:
http://www.crucial.com/store/listparts.aspx?model=Dimension+E510
The Dimension E510 can support up to 8gb of RAM [4 x 2gb modules], but if a 32-bit operating system is installed, this will see and utilize, only 3gb or 3.5gb. To utilize more memory, a 64-bit version of the operating system is required.
Bev.