How to edit DVD using Windows Movie Maker?

I converted all my old VHS movie to DVD now I want to use Windows movie maker to edit them, but when I upload the vob file, it just upload the video but not the audio. Can you help me to fix this problem? should I convert it to another format? what software should I use to do so? or do I need to use another software to edit my vob file?
please suggest me free and user friendly software...