To remove a user account from Lync Server

1. From a user account that is assigned to the CsUserAdministrator role or the CsAdministrator role, log on to any computer in your internal deployment.
2. Open a browser window, and then enter the Admin URL to open the Lync Server Control Panel. For details about the different methods you can use to start Lync Server Control Panel, see Open Lync Server Administrative Tools.
3. In the left navigation bar, click Users.
4. In the Search users box, type all or the first portion of the display name, first name, last name, Security Accounts Manager (SAM) account name, SIP address, or line Uniform Resource Identifier (URI) of the user account that you want to disable or re-enable, and then click Find.
5. In the table, click the user account that you want to remove.
   

   Note:
   If you want to select multiple user accounts, press and hold down Ctrl, and then click each user account in the list that you want to remove. To select a range of user accounts, press and hold the Ctrl key, click the first user account in the range, press and hold down Shift+Ctrl, and then click the last user account in the range.

6. On the Action menu, click Remove from Lync Server.
   
   http://technet.microsoft.com/en-us/library/gg195816.aspx