If I have my VIDEO and AUDIO VOB files already encoded using another software than ENCORE, can I still make the menu part in Encore and use the vob? Thank you.
No idea. I don't even know what Authoring Works 5 is, and I've been doing this for a living since the days where you had to explain what a DVD was.
What you really need to do here is use a program that can encode and author, or use a separate encoder that generates MPEG2 and .ac3 files to import into your authoring software.