Well, firstly I'm not familiar with WMM so can't discuss what specific options it may or may not have but...
...my experience of interlaced signals is that unless you have a 24p option on your camera then you will get interlacing.
Rather than de-interlace as the first step, if I'm going to bother at all then I leave the deinterlacing till after I have edited my movie and tick the de-intrerlace button in my 'export' dialogue box.
You didn't mention what you delivery system is. Web broadcast ro are you building DVD to watch on a TV? If the latter then you're likely just as well to leave the intelacing in there as standard TV will expect an interlaced signal.