no you can't.
sorry i hadn't realized what you've done there... you initially had socket 939 proc/mobo.. which woulda been incompatible with the DDR2 ram.. so if you get that AM2 motherboard, and instead of 939 X2 3800+ get the AM2 3800+ it will be all good.
socket am2 processors for socket am2 motherboards ~ which uses DDR2
socket 939 processors for socket 939 motherboards ~ which uses DDR
ah and there should be no price difference between socket 939 and AM2. perforamnce is pretty much the same... except AM2 is newer.
"Is virtue a thing remote? I wish to be virtuous, and lo! Virtue is at hand." -Confucius