+1 bucknutty
You can check chipset compatibility at http://ark.intel.com/products/27520/Intel-Pentium-D-Processor-945-(4M-Cache-3_40-GHz-800-MHz-FSB) and then click on compatibility then chipsets. Really if you are going to upgrade then you are going to want to at least move up into the Intel® Core™ 2 Duo line of processors but that would require that you upgrade your motherboard and most likely get a new OS since Dells OEM Windows doesnt like to have the board changed.
Christian Wood
Intel Enthusiast Team