If you are a Siemens WinCC user (specifically version 7.5 or similar), few errors are as frustrating as the ominous message:
An incomplete or failed installation of the Microsoft SQL Server instance used by WinCC. Software Conflicts: Coexistence with incompatible software like WinCC Professional (from TIA Portal) on the same machine. User Permissions: The logged-in Windows user is not a member of the local "SIMATIC_HMI" user group. Special Characters: a basic application could not be started wincc 75
The error sometimes lives in a shared component used by TIA Portal and WinCC. If you are a Siemens WinCC user (specifically version 7