KB2688964 - FIX: Error message when you use the SQL Server 2012 ...
Resolves an issue that occurs when you use the SQL Server 2012 installation media to upgrade, to repair, or to uninstall features
Uninstall or remove apps and programs in Windows
There are different ways to remove apps and programs, so if you can't find the one you're looking for, you can try another location. Note that some apps and programs are built into Windows and can't be uninstalled.
KB2861939 - FIX: Cannot uninstall, repair, add new features to, or add ...
Fixes an issue in which you cannot uninstall, repair, add new features to, or add a new instance to SQL Server 2008 or SQL Server 2008 R2 on Windows 8. This issue occurs when the computer does not have the .NET Framework 3.5 installed.
Fix problems that block programs from being installed or removed
The Program Install and Uninstall troubleshooter helps you automatically repair issues when you're blocked from installing or removing programs. It also fixes corrupted registry keys.
List of security program cleanup and uninstall tools
Provides links to the uninstall tools and directions for many security programs.
KB3189033 - FIX: Cannot uninstall service packs for SQL Server 2014 ...
Fixes an issue in which you can't uninstall service packs for SQL Server 2014 after a cumulative update is installed.
KB3011867 - SQL Server in-place upgrade fails if the there's no JOBS ...
For example, if you are upgrading from SQL Server 2012 to SQL Server 2014, use the SQL Server 2014 setup media. Copy and run the command from step 2 at a command prompt in order to remove the partial installation.
You cannot add or remove features to a SQL Server 2008, SQL Server 2008 ...
The option to add or remove features is not supported either when you run the setup through SQL Server Installation Center or when you run the setup from a command prompt.
KB2446036 - FIX: MOF compilation errors occur and Setup fails for SQL ...
Fixes an installation issue that occurs when you try to install SQL Server 2008 or SQL Server 2008 R2.
KB2387686 - FIX: "A MOF syntax error occurred" error message occurs ...
You must apply a SQL Server 2008 Service Pack 1 hotfix to an installation of SQL Server 2008 Service Pack 1. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.