The Specified credentials that were provided are not valid.

SQL SERVER || The Specified credentials that were provided are not valid.

      

Root Cause of the error →
This issue arises when the "Account Name" is not selected in the "SQL Server Database Engine" row under the "Server Configuration" page.

      

Solution →
To resolve this, simply click "OK" on the error message and select the appropriate "Account Name" in the "SQL Server Database Engine" row.

By meticulously following this step, you can rectify the error and successfully install SQL Server 2008 R2 SP2 Express Edition.