OK, here goes.
Google "windows movie maker convert .mov to .avi no sound".
Apparently, when a .mov file is made by a camera, there are different codecs used to creat the video and the audio. When WMM converts the file to .avi it uses default codecs to convert the video and the audio. You need to know what codec to use on each one and to do so you need to know what codecs created each one.
Evidently the video codec being used to convert the video is working.
Follow the links in the google search and it gives some programs that will reveal the codecs for a file that was created. Then you can set the converter to use the proper codecs for conversion.
I wish I could give an explicit answer to your question but that is what I found reading the search results. I'm afraid it is not going to be as easy as one would want.
The easiest answer I found was this:
The full version of Apple QuickTime can
convert the .mov files.
Just as an experiment...try converting one
of your .mov files at the following online site:
Media-Convert
Media Convert - free and on line - convert and split sound, ringtones, images, docs -
Apple Quicktime conversion instructions
1) In the "File" field...click the "Browse"
button and navigate to the .mov file you
wish to convert. When you select the
file...the path will appear in the 'File' field.
2) The "Input format" field should automatically
show..."Apple Quicktime (.mov)" leave it
as is...
3) "Output" format has two drop windows...
the field on the left will display, "No video
preset"...leave it as is...
4) In the next drop window to the right
you can choose the format you wish to
convert to...try:
Audio Video Interleave (.avi)
5) Left click the blue *OK* button.
Now...wait for the file to be converted.
(be patient)
When the conversion is complete you will see:
File successfull converted !
Left click the Download button...the Save As
screen will appear...left click the Save button /
Choose a folder to save in...left click the Save
button. When the file is downloaded you should
be able to play it with Windows Media Player
and it should be compatible with Movie maker.