By following the steps described, you can have both SQL Server 2005 and 2008 installed on a machine at the same time. The trick is simple, just change a Registry directory name of SQL Server 2005 Studio with the Registry editor. After the installation, you can then change it back.
- Go to Windows > Run, enter “regedit” and click OK.
- Browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsft SQL Server\90.
- Rename “90? to something else, like “old”.
You can now rerun the process in SQL Server 2008 Express installation wizard. After installation has completed, you will notice that the old SQL Server 2005 doesn’t run when you try to launch it. No worries, to fix it, you can change the newly created directory “90? to “70?. Then change “old” that you changed from “90? before back to “90?. It should now work for both SQL Server 2005 and 2008 Studio Express.