Honestly? I'm not sure it would be worth the money to even ship it somewhere...
With machines like that you /may/ be able to find someone to take it like a school or library or find some place you can donate used computers. Or maybe to a desperate friend? Though it being in non-operational condition... maybe not even then. It really is pretty much recycle material.
I've thrown away (recycled of course) more powerful machines than that. :/
But try looking up P4 800 2gig ram on ebay and see what people are getting (realizing that those are probably mostly still working machines)