well both of the methods don't work.
the error doesnt have anything to do with th ip adresses. i once made a lan-party @ my home, and we were 10 people playing with the same ip.
virtual machine doesn't work either...
there are no graphic acceleration drivers for virtual pcs.. so u cannot run any direct3d applications on a vm. and even if there were some, it would be impossible for one pc to load 2 operating systems + loading 2 games + calculating the graphics on both games... u would need a really really expensive pc