to load HALO NMP you must load HALO first. HALO NMP should be under Settings on HALO main screen.
in the HALO folder you should have
bink folder - has videos of HALO
maps - maps for normal HALO
NMP - maps for HALO NMP
default.xbe - xbe for HALO
HaloNMP.xbe - xbe for HALO NMP
If you followed all the instructions , the ui.map file in maps folder should be patched with the patching file provided , also the default.xbe , unless you got an already built version.