Quote - "Why actually not copy the old content "over" the freshly installed version?"

Well, it's safer this way, the risk of ruining anything is zero. Anyway, if you copy it over, make sure you don't copy any of the binaries because these are different in Vue depending on the OS version (32 or 64 bit).

How to point to another folder in Vue:
In each of the dialog boxes for "load object", "load atmosphere", "load material", "load function", etc, etc, you have a tiny little button with a blank page that says "new collection" when you put your mouse over it. Just click there and point to the copied folder. You have to do this for each type of stuff (object, atmosphere, material, etc).