Oh, and a couple things I wanted to make clear...

Just because you see it on your computer's screen doesn't mean it's actually a problem in the video file itself. It might be only happening at playback time. If the video files you're working with are interlaced, and they're staying interlaced as you capture, edit, compress, and play them, then maybe it's only the actual process of playing back the interlaced video to your computer's progressive-scan screen that's causing the combing.

If the first capture file off of the camcorder is genuinely combed, then your capture process needs to do something about deinterlacing the video better. Or, possibly, you might need to simply tell all the bits of software (from capture all the way through to final edit) that you want them to stay interlaced the whole time and don't even TRY deinterlacing. That way the final playback (let's assume it's a DVD-R) will look right on your parents' interlaced television set.