searched on this long time ago and recently.
there isnt such a thing.
didnt liked WinMo that much, but i'd love to run Garmin Mobile XT for WinMo 6.5 on N900.
WinMo n N900 all use ARM, but hardware drivers (where does WinMo latch to for file system, camera, etc?)
it may be possible to modify Wine (Windows emulator) for N900 to emulate WinMo but i think no developer's motivated.
the whole gnu linux environment in N900 is much better (to me at least) anyway.

kh