Whenever the Lync /MOC client is started up, it will register protocol handlers for the callto and tel protocol (so you can click on a link like this: callto://tel:myphonenumberhere, or tel://tel:myphonenumberhere (the requirement for tel: is actually new in Lync... OCS merrily dialed callto://+1234567)).
This is fine if you use Lync/MOC for calls - but if the client is used for IM/Presence only, this is very undesirable as those protocols are industry standards, and the user might have another client running on the PC with which he/she wants to make calls (e.g. Skype). So, how do you stop Lync/MOC from automatically assigning itself as handler for the callto and tel protocols?
And while we're at it.. does anybody know how Lync manages to rewrite those keys when they are deleted? Accessing HKEY_CLASSES_ROOT requires admin rights.. but my Lync doesn't run with admin rights and still manages to take those keys back.