Honestly, at this point, I would recommend a complete upgrade. If you JUST want to upgrade the board, you will likely get very limited time on a replacement of similar or even slight upgrade. That's a socket 478 motherboard and 478 is 2 generations behind current sockets. We are on the third generation socket AFTER 478. If it was a socket 775 that supported a C2D, trying to squeak another year or so would be fine (I'm currently using a C2D e6750 & Gigabyte P35 board to write this) but, 478 is just a bit too old.
You can probably find a 775 combo that can just drop into your setup for fairly cheap (~$75 or less) if you would like to stick with skimping on the options but, you do need to upgrade socket/proc. at least, if you want something decent. Let us know if you need suggestions/help looking and I'll see if I can find something.