intel now uses socket 775 i think so if you want to upgrade your cpu aswell as your mobo then go for this socket.
if you want to keep your current cpu (and at 3.4ghz i would keep it for the mean time as its by no means slow) then i would keep your current mobo too unless its dead. why do you wish to upgrade it? there are lots of socket 478 boards to choose from if you need to. what do you want from the new mobo and what is your current board please?