And is the extra power connector hooked up as well it should have one if it is an AGP gfx card, the PSU should certainly be enough to power it. The fact that even with no drivers it the new card doesnt work but the old one does work doesnt bode well.
It sounds to me like a bad card or it was accidently damaged during the installation here is some information on static its a common way to fry things accidentally http://www.pccompute...com/esd/esd.htm
The ram wise yes they should be two sticks of the same size if he was running dual channel memory however that feature wasnt introduced until the socket 939 motherboards and chips, he has a socket 754(from what i could gather on the motherboard), so it should be fine.
Compatibilty wise it should work, he should have an AGP 8x version of the card and has sufficient power and a compatible motherboard. And while the motherboard is generally not considered a good motherboard from what ive read thats just down to it being a bog standard budget board rahter than there being any flaws in the board. This is leading to me thinking its card damage, the best way to rule this out would be to try the card on another compatible system and see if you get the same error, if you do its a faulty card(happens in electronics) if it works its something in the computer thats wrong and we can probably track it down and fix it.
So if you followed my advise on the drivers and its still no go i would test the card or just take a chance and RMA it and get a new one under warranty, liklehood of two broken cards is relativley low(not impossible but low).