NERO - Create DVD-VIDEO problems please help

i have a bunch of karaoke DVDs, i ripped each songs out and saved the VOB files. I’m trying to make my own Karaoke DVDs but i have no luck with any other software but NERO. I use nero “StartSmart” and click on “MAKE YOUR OWN DVD-VIDEO.” After i have imported the VOB files, i can only get ONE audio from the VOB file instead of two. One with vocal and one without. So the question is: HOW DO I GET TWO AUDIO IN THERE?

If anyone know a better software to do this please let me know. I’m using Nero 6 right now and thinking of upgrading to 7 to see if it will let me do what i need to do.