Taking the sound from a video file

It depends on format, but you can use VirtualDub for avi-files. http://www.virtualdub.org

The files will become a lot smaller, because video takes lots of more space than audio. At least if you want decent quality.

Re: Taking the sound from a video file
My creative labs sound blaster came with recording software that can record what you are hearing on your speakers. It records it in stereo, so I can pick up sound bites from video that way. If you have a soundblaster card you may already have the software that you need.