When you are evaluating the Lync server and you want to upgrade or install the full version, you can do it easily without re-installing or reconfigure the service. You can also upgrade when your evaluation has expired.

If your evaluation has expired, you will notice that you Lync Front-End Server doesn’t start and you will see the Windows could not start the Lync Server Front-End on local computer error showing. To confirm this, you must go on the Lync Server section on the Event Viewer and see that it is complaining about the license as below.

The evaluation period for Microsoft Lync Server 2010 has expired. Please upgrade from the evaluation version to the fully licensed version of the product. Look at help for Setup.exe to learn how to upgrade from evaluation version to the licensed version.
Cause: The evaluation period for Microsoft Lync Server 2010 has expired.

To upgrade to the full version you need to download the setup in your server. Then open the Lync Management Shell and enter the below.

Get-CsServerVersion (This will show the current version of the system)

Browse to the location of the installation of the full version example C:\LyncFull\Setup\AMD64\Setup and run the below command.

msiexec.exe /fvomus server.msi EVALTOFULL=1 /qb
Enable-CsComputer

Once ready enter again the Get-CSServerVersion to verify that the version has been updated.

Note: This must be done on all servers of Lync i.e. Director, Front-End and Edge