Copy 3 mini-DVDs on one regular DVD

Hi everybody:

I am trying to copy three mini-DVDs on one regular DVD. Capacity is fine, so there is no need in compressing.
I tried several times with Nero Vison Express but a big problem came up. Nero wanted a DVD-Video Plug-in to be instaled, with a cost of thirty euros. This plug-in is said to give you dolby@digital. As I recorded without this plug in, my recording was mute! I dont need dolby, I just want sound. Does anybody know how to archieve this?
Thanks
Alfonso