The following error will occur during the SQL install portion of the SMS version 4.2/4.3 upgrade on a system with SMS version 4.02 and SER v 7.2 : A component that you have specified in the ADD_LOCAL property is already installed. To upgrade the existing component, refer to the template.ini and set the UPGRADE property to the name of the component. To avoid this error run the Windows Installer Cleanup Utility from Microsoft (Microsoft KB article 290301)
SMS 4.2/4.3 is attempting to upgrade SQL 2005 Express Tools, but does not have permission.
Download and run the Windows Installer CleanUp Utility from Microsoft KB article 290301. https://support.microsoft.com/default.aspx/kb/290301
Run the utility from programs, select and remove SQL 2005 Express Edition Tools, then re-run the SMS Upgrade. (Note that SMS upgrade will install SQL 2005 Tools)