Project 2007 Compatibility Mode is enabled by default for an upgraded server and allows Project 2007 clients to connect to ...

Project 2007 Compatibility Mode is enabled by default for an upgraded server and allows Project 2007 clients to connect to the server.  If all the Project Managers in your organization are using Microsoft Project Server 2010 and you have upgraded the applications that are running on top of Project Server to be Microsoft Project Server 2010 compliant, you can turn this mode off to enable all the new features.