How to delete "Lync Contacts" in Outlook 2013？

Hi,

I'm using Lync 2013 and outlook 2013, the backend system is Exchange Server 2013 and Lync Server 2010.

I found that in Outlook 2013 People tab, there's a "Lync Contacts" folder under "My Contacts", which is created by Lync 2010 client enabled by option "Save my Lync contacts in my personal contacts folder on Exchange", and when I want to delete any contact under "Lync Contacts", a pop-up windows displayed and said: you cannot make changes to contents of this read-only folder.

I reinstalled Lync 2010 client back, and check the option "Save my Lync contacts in my personal contacts folder on Exchange" is not selected.

So, anyone can tell me how to delete the "Lync Contacts"?