Upgrading the operating system of an existing installation of Lync Server 2010, or running Lync Server 2010 Group Chat Server are not supported with Windows Server 2012.
After publishing your topology, installing Lync and trying to login to the Lync control panel for the first time you will see the following message.
A 404.17 - Not Found error message.
This is because the IIS Application Pools are using the .NET Framework Version v4.0 by default. This is displayed in the Application Pools configuration in Internet Information Services Manager.
Application Pools using .NET Framework Version v4.0
So, to fix the issue simply set all application pools named "Cs"-something to use .NET Framework Version v2.0 instead and then open a command prompt to issue an iisreset command.
Application Pools for Lync 2010 should use .NET Framework Version v2.0
If you now have your Lync Control Panel window still open, just hit refresh and the Control Panel will display fine.
For more info:
404.17 - Not Found error message