Its a Socket 939 board, but those are hard to come by (outdated), I don't think Newegg even stocks those anymore, might want to try to get an old one of eBay or Craigs)
so if you upgrade...
you'd have to change the following:
- New board
- New CPU
- New RAM (Socket 939 uses DDR newer ones come in DDR2,3)
EDIT: forgot to mention a need of a budget