What motherboard and processor can i get?

You will probably have to source these 2nd hand, socket 478 mobos and CPUs are now basically obselete have been discontinued for quite a few years now, you'll have a hard time finding new stock of these. I gotta ask why do you want to waste money on this? If you are keeping this PC alive for the sheer hell of it then that's fair enough, but if that's not the case you're better off saving your money for a whole new PC, especially if you are happy to build it yourself you could get something rather decent for not alot of cash