What's the best processor I could put in an old Compaq Evo?

[zephyrprime]

I got an old compaq Evo with no processor in it from work. It has a mpga478B socket on it and it uses SDRAM. I can't see what chipset it has and there have been lots of very different models of EVO produced by compaq over the years so pinning down exactly what it is from compaqs site was a fruitless endeavor for me. Anyone have any idea what can be put into this thing?