Problem

When you try to run the installer for System Center Configuration Manager 2012 R2 to upgrade from 2012 SP1, it fails with the following error message in the setup log.

INFO: Setup detected an existing Configuration Manager installation. Currently installed version is 7711~

This is stating that you have a pre-SP1 build and cannot continue, even though later in the setup log, it reports:

INFO: Configuration Manager Build Number = 7958 

which indicates that you are running a later build of 2012 SP1 (including CU5).

Reason

If you search the registry for string '7711', you should come upon keys in HKLM - SOFTWARE - Microsoft - SMS - Setup with the following data.

This tells us that the Admin Console is installed on this server is on a release older than 2012 SP1, however if we check the installed program details in Windows Programs & Features, we see the following:

 

Solution

The solution is to either remove the Admin Console from your server or manually update the registry keys for 'UI Version' and 'Version' as shown above. In this case, it was updated to '7804' to match the build that was installed. After this the upgrade completed successfully.