If you manage to compile Qt3, I think that's the way to go indeed. IIRC there is MSVC2003 patch from the Q..Win project, not sure about MSVC2005.
I did not try that route. It should work though.
You will have to port Aspell to MSVC. The good news is that Peter K. has already done so. The bad news is that the patch is against Aspell-cvs.
I have never been sussfully on aspell/win, mingw/vc/6.0/cvs whatsoever. :-( Bo