The following error will occur during the installation of SCCM 2012 if you ever changed the system name after the installation of SQL Server:
The SQL server name specified during setup must match the Name in sys.servers of the SQL server
To solve this issue, open the Microsoft SQL Server Management Studio, and run the following query:
EXEC sp_dropserver ‘your old server name’
EXEC sp_addserver ‘your current server name’, ‘local’
To find out what your old computer name was, according to SQL, you can open the logfile of Configuration Manager Setup at c:\ConfigMgrSetup.log. Search for sp_dropserver and you’ll see the old name.
After you’ve executed the query, reboot the SQL server.
Then re-run the SCCM installation wizard. It will first only give you the option to uninstall the site. After having done that, you’ll be able to install SCCM 2012.