Well, personally I don't see the point in laying down extra cash on a platform that is nearing the end of its operational life-cycle. Buying a stick of DDR 400 ram at around $50-$60 USD isn't really good value IMHO, especially considering it will have a minimal effect overall on hos PC's performance. I mean add around $100-$120 and you get a viable x2 platform and 1 gig ram.
http://www.newegg.com/Product/Produc...82E16813135039
$101 x2 3600+ and mobo although the PCI slot only runs at x8 it's not a massive issue unless you're plonking in a 7900gs or higher. (Although I've chucked an x1950pro in a similar mobo and the difference was negligible.)
I'm looking a his mobo and well, there's not a lot of life in it, I mean AGP is dead, DDR is dead.
if he wants to stick with his p4 LGA775 well
http://www.newegg.com/Product/Produc...82E16813186111
and
1 gig of ddr2 667
http://www.newegg.com/Product/Produc...82E16820146580
for something like $70 total. he can reuse his P4 LGA775, HDD, DVD. I feel it not worth it to spend $50 on ddr ram, when for $20 more he can get a new mobo supporting ddr2 ram, and 1 gig of ddr2 667