I hope your not trying to flash a,sequent rom on the N860 cuz its not gonna work in fact your gonna brick your phone.
Flashing a warp 2 rom on a warp 1 rom would be something explained like this since I can't break it down in how you will screw your phone up but............. ( roms has to be phone specific. installing roms for a different phone would cause all sorts of fun problems. it has to know how to communicate with the screen or you get no picture, it has to know how to read the internal and external storage to install roms, and every phone works a little differently. think of it like this, its basically a driver issue. just like your computer, if you try to install ati drivers for your nvidia card its not gonna work. try getting an hp printer to work only using epson drivers, not gonna happen. and they cant just throw every possible driver combination on a phone to make it compatable with every phone out, yes that would be great but it would be so massive that it would take forever to work even if you could find a way to make it fit which with the amount of storage they give you is impossible