[DanielG]

DVDShrink will allow you to do combine 2 dvds onto 1 disc (as long as there's enough room on the disc)

To merge two movies on the same dvd follow this procedure. Remember: in this way you don't keep any menu, but only movies.

1) Open the first movie with dvd shrink

2) Press "Reauthor" button

3) Select all items from first movie that you want keep and drag to left panel (don't select menus: they will be lost at all in reauthor mode)

4) From "DVD browser" tab select the second movie

5) Select all items you want to keep from the second movie and drag them on left panel under previous selected items (again, no menus)

6) Press "Backup" button

7) Select output format (ISO or HD folder)

8) That's all.

Above instructions stolen from: here

You can get DVD Shrink from here: http://www.dvdshrink.org/