Is there a way to add audio to a video?

OK, here is the problem. My daughter was in a competition and we purchased a dvd of her performance and the dvd we received from the video company has no audio...only video. They said they had a problem with the audio recording equipment. So, my question. Since I have the audio (song) she used, is there any way I can rip the video from the disc I purchased of her performance and then somehow add the audio to it and burn it back to dvd?

Crazy...I know...but what do you do?