Sorry, nothing in 939 will let the card run to it's full potential. It's an outdated socket.
The closest you are going to get is an opty 165 or X2 overclocked to the max.
if he upgraded to 2 gigs of ram and got a 4200x2 it would be just fine.
Oh and am2 has one more pin...940pins as compared to 939 for (duh) 939 systems.