the socket 478 was an older intel proccessor socket and if my memory serves me right sli was not even out nor was pci express even. Finding a socket 478 motherboard with sli will be almost impossible if not impossible. Like badge said as of right now you need an nvidia chipset for sli but even if such a chipset existed on socket 478 your gpu would be very badly bottlenecked by the old p4.
a quick check of newegg revealed that there is a 478 mobo that has 1 pci express graphics port so if you want to upgrade to that mobo it would work with a 4 processor.