Here are the specs on my OptiPlex 330
CPU: Core 2 Duo E8400 @ 3.00GHz
GPU: NVidia Quadro 4000 2GB DDR5
HHD:1x 500GB Waster Digital, 2TB Seagate, and 2 DVD+ Rom
I want to know if I can upgrade the ram since I upgraded the CPU it had before a Core 2 Duo E4500 @2.20GHz
Max RAM on that model is 4G, so you're al the limit.