Finally got it to work. How? Don't know!
Tried five things:
1. Did an EXPORT from REGEDIT
2. Upped silder for UAC by one ... got MANY windows warnings & ERUNT didn't work - so changed slider to bottom (ie UAC 'off')
3. In ERUNT checked box for "other open ...' - didn't work (didn't expect it too)
4. Unchecked above - got initial err the file coundn't be created
5 Ran ERUNT again - it worked !! (still get err that initial file not found, but always got that err)
So bottom line it works now ... but not sure why.
If anyone reads this, all I can say is keep trying different things