The motherboard in the machine is an MSI P4N Sli using the old Nforce4 Sli chipset so C2D isn't possible on that chipset on any board.
As far as the futility of the upgrade, I know. Trust me, I know. It took me an hour and a half of my time just to convince her to allow me to upgrade her CPU and GPU since she is trying to play newer games on that crap box anyways.
She is one of those paranoid people that swore for starters that she needed the Corsair GS700 700w PSU she paid $200 for installed @ BestBuy and swore she might even need a 1kw PSU. She also is too worried about losing her programs for school even though I told her I can generalize the OS and make it boot under a new mobo and it would just need the OS re-activated but she just won't let me upgrade her mobo to something that takes a C2D :-/
Some people you can only help so much