Need codec for Win Movie Maker 6.0 Vista

I've used Movie Maker a little with my own videos, but I'm still very new to this.

Now I want to extract a short clip from a 50-minute MPEG-4. Movie maker says it needs a codec. I more or less know what a codec is, but only in principle. I don't know where they come from: do I expect to buy them or find them from Microsoft, or what?

I've tried looking for them, but there's a lot of details I don't understand -- it seems they are advertised for many different versions of Movie Maker, let alone other software. How will I know I've found one that's usable?

What do I do to install one of these?

Any help appreciated.

 

I think this is about this issue: http://www.windowsmoviemakers.net/PapaJohn/70/Render_MPEG-4_Movies.aspx
Microsoft: http://www.microsoft.com/windows/windowsmedia/forpros/format/codecdownload.aspx
You could also convert the MPG4 before extracting: http://media-convert.com/

The last option is the easiest one.

 

Sorry - forget link number 2. This could also be of help: http://www.microsoft.com/windows/windowsmedia/forpros/encoder/default.mspx

 

http://www.free-codecs.com/download/FFDshow.htm