IMHO, he should return the Prescott, and possibly rebuild the machine.
There are great ASRock "dual" series motherboards out there, that would allow him to make that transition as painless as possible: AGP and PCIe (4x, but still...), DDR and DDR2 (667MHz), 20-pin PS connector etc.
All you might need is a $60 MB and $130 CPU (maybe cheaper after tomorrow!) - the rest can be reused.
ASRock 4CoreDual-VSTA:
http://www.newegg.com/Product/...x?Item=N82E16813157107
Intel Core 2 Duo E4400 Allendale 2.0GHz 2M shared L2 Cache:
http://www.newegg.com/Product/...x?Item=N82E16819115014
For ~$200.00 he can easily double his system's performance.
BTW, I am using the ASRock 775Dual-VSTA right now with the E6600 CPU, 2GB of OCZ PC5400 DDR2 (replaced my PC2700 DDR, only had 2x512MB modules), BFG 7800GS AGP Video Card, old Antec True Power 480W PSU with 20-pin MB connector.
Flawless, my wife is playing games like Sims 2 at 1280x1040 with all the settings max.