Audio noiseless video becomes noisy after importing in windows movie maker
Try seperating the audio and video streams of the WMV and AVI files - I don't have an app in mind but there should be some free ones avaliable. Put the video part in, which will remain in the original format (WMV or AVI) and should work. For the audio, use Soundbooth to convert it into a variety of formats like WAV, MP3, WMV, etc. until the import works without noise. I don't use MM now, but I have before and know for a fact that there are no problems with importing MP3 files.