This is a great PC. Very easy to work on, parts are cheap, takes only few minutes to change the mobo...
His PC is upgrade ready. No motherboard replacing is necessary.
1. Quick Search on Dell Support Forums
here indicated that your PC compatible with 1066MHZ Intel Core 2 Duo CPUs
2. The Official Dell Mobo specification confirms this
here (it is Intel G965 based board btw).
3. Download and install the most recent BIOS Upgrade for your Dell
here prior the CPU upgrade.
4. Get the E6400
here, but I think that the Allendale core based C2D cpus will work as well
available on Newegg No matter what they say,
any C2D cpu is a significat upgrade over the Pentium D proc.
5. This Radeon HD4850 is a single slot type of a card. I know that the 8800GT will fit in this PC just fine, so I assume that this card should fit as well
Newegg Link + Rebate
If you are an Nvidia fan, there are some 9800GT cards that are available in a single slot configuration like this
PNY
6. Your 600W PSU should support both HD4850 and the 9800GT
7. Your PC will support up to 4x1GB of DDR2 800 RAM
8. Don't forget to apply a thin layer of a thermal compound between the massive heatsink and your new CPU - I really like Artic Silver 5
