Second monitor will not show

It sounds like the nView is working ok, as the default is "clone"...
I don't think you have mentioned what screen setting you have set
nView to, but within the nvidia settings tab of advanced screen
properties, there should be a drop down box to say if you want to
clone, split horiz, split vert, have 2 screens, or whatever. Have you
tried these?

Yes - in the nview menu all these otions show up - except that I can
only choose from "TV + Analog Monitor"
A "Digital" does not show up...

It does not seem to matter, what resolution I use...

as i mentioned before - I did do several clean uninstalls - except
when I first exchanged cards:
My asus p4p800 was exchanged on warranty to p4p800SE - which does NOT
allow for "old" 4xAGP.
After changing the board, I did try to boot once with my old G450
Matrox Dualhead - no luck there, of course. After finding out about
the SE restrictions, I bought the Geforce card.

Both monitors lit up right away - installed the new drivers -
everything seemed perfect - except for that second monitor on DVI - it
just will not show in any of the config menus.

I would hate to have to do a clean XP install.