Re: Windows Movie Maker Takes Forever to "Prepare Video."
You can't disable the function. If you're importing the video to edit, than it's splitting it into frames, and separating the audio. If you're exporting the video, then it's compiling the frames and combining the video/audio to a single file.
You may want to try AVS (never used it myself) as EchoNatek suggested and that may be a little faster.
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?