Thanks for prompt reply.
Unfortunately that didn't change anything. Made modification to Enforce by user, confirmed that users have "Allow Anonymous Participants" not checked. Again, MEET NOW directly from the LM client (with OCS 2007 Enterprise), creates the key
HKCU\Software\Microsoft\Live Meeting\Preferences\Server\AdmissionPolicy=anonymous
I really don't know if this is driven by LM client or OCS server.
Any hints are appreciated.