I've a Dell Precision 470 and upgraded it from a 2.8Ghz single core to 3Ghz dual core (as in 2 x 3Ghz). Now I'm no expert but I know how to follow the instructions from Dell which basically said plug in the CPU, plug in the VRM and switch it on.
That done, everything appears to be functioning, both CPUs are listed in the BIOS and it lists them separately when running benchmark software.
It seems a bit faster, there's a noticeable difference but it's not as fast as I'd expected and when I go to 'My Computer>Properties' it says it's a 3Ghz computer. I'm not sure if I've missed something and wondering if I had to change something in Windows.
It would even be a great help if somebody out there who has a dual core could look up there system to see if thier computer lists one or both cores.