I'm looking for some video sound amplification software...?

I've recently converted some old 8mm video tapes to MPEG-2 files. They look great, but the volume level is really low. I would like to be able to amplify the audio track and save it to the video. This would create a much nicer and louder movie for me to burn to DVD. I've looked at some 'freeware' programs, but I'm not having any luck. Any ideas?