If you are getting this error then one probable reason can be that you are trying to install Sql Server 2005 SP1 on a machine already having Sql Server 2005 SP2 Installed on it.
This error might be followed by another error telling "SqlSupport.msp is not digitally signed"
The best way to fix this error is by following these steps:-
- Save the data in the following Registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\90\Bootstrap\MSIRefCount\Uninstall
2.Copy this value data in a text file and save it for future use.
3.Go to control panel , add/remove program and remove the Microsoft Sql Server Setup Support Files.While uninstalling you might get some error message or warning that this uninstall may effect some other Sql Server Components which are already installed.
4.Click Yes to uninstall on the error message.
5.From the installation CD browse to the folder Tools\Setup and start the SqlSupport.msi to again install the Sql Server Setup Support Files
6.After this step again browse to the registry location mentioned earlier and change the data value to the one we saved in the text file.
7.Now you can successfully start the install of Sql Server 2005 SP1