This is a rather sensitive topic here at MyCE. We support those who want to make backups of dvds, blu ray or even legally obtained digital copies of movies, but the vast majority of videos found through torrents are not legal, and are thus, not a topic to be discussed here.
You should look through our guidelines to copyright protected material: http://club.myce.com/f34/guidelines-copyright-protected-material-316049/
You haven't mentioned any specifics, so you are safe for now, and I'll assume for the moment that you have found something legal to download. The first thing to do is check the original file and see if there is any distortion in the audio there, which you seem to have done.
If the original file plays correctly, then you are getting something screwed up in Windows Movie Maker. I'm not sure why you are using that program in the first place. You're actually trying to make .wmv output files? Or is the output being passed to Windows DVD Maker and you are getting finished dvd-video out of it?
In either case, I'd stop using these for anything. If you want a finished dvd-video from various types of video files, you should use a free program called AVStoDVD, or a similar one called DVDFlick. I prefer AVStoDVD, but it may not be quite as friendly to use for newcomers as Flick. Both can be set to burn directly to a disk using ImgBurn ( a free burning program that is included).
I would download and install ImgBurn separately, open it up and click on any of the options. Then set burning speed to 8x or 12x...no more. The setting will be kept when you use ImgBurn from within AVStoDVD or DVDFlick.
Of course, you may not be trying to get dvd-video. In which case you'll need to explain exactly what you are after.