When I try to install a new instance of SQL Server 2008 Express on a development machine with SQL 2005 Express already up and running, the install validation fails because t
Just Remove the the Workstation Components from Add/Remove Programs - SQL Server 2005. Removing Workstation Components, SQL Server 2008 installation goes well.
I'am trying to install SQL SERVER developer 2008 R2 alongside SQL SERVER 2005 EXPRESS,
i went to program features, clicked on unistall SQL SERVER 2005 EXPRESS, and only checked, WORKSTATION COMPONENTS, it unistalled: support files, sql mngmt studio
After that installation of sql 2008 r2 developer went ok....
Hopes this helps somebody
If you currently have Red Gate SQL Toolbelt, you will need to unistall that too before continuing. Somehow it adds a reference to the 2005 version of the SQL Management Studio.
I had to unistall the Workstation Components and SSMS Tools Pack (SSMS Tools Pack is an add-in for Microsoft SQL Server Management Studio (SSMS) including SSMS Express.) Installation of SQL 2008 is now proceeding as it should.
In my case even after uninstalling all 2005 related components it didn't worked. I had to resort to a brute force way and remove following registry keys
32 Bit OS: HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\90
64 Bit OS: HKLM\Software\Wow6432Node\Microsoft\Microsoft SQL Server\90
I also had to remove the SMSS before it would get past that step.