How do I make copies of an already made dvd on Windows Movie Maker?

I made a slide show movie with WMM and put it on DVD and I need to make 20 more copies for my group. Only thing is I messed up and cannot open the same file again and there is no way I can redo the entire 35 minute movie over again. I did make one copy. How do I get the copy on to my computer and back on to WMM to make more copies for my group. It's in DVD format and I want to put it in WMA or MOV or AVI format. HELP PLEASE!!!! Thanks..