As I mentioned in a prior post, VS Database Professional CTP5 requires you to install SQL Server Express as part of the setup. On my current project I just started to do some database work so I really wanted the CTP installed, but I didn't want to install SQL Server Express on my virtual machine since I already have a full blown SQL Server installation running. So with some help from Regmon I figured out what registry key the installer was looking for.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL]"SQLEXPRESS"="MSSQL.1"
Now run the installer again and it should skip the SQL Express install. You will have to change some settings in Visual Studio under Options -> Database Tools -> Design-time Validation Database to be the correct SQL instance since you won't have express running. Also, you can delete the registry key once you get everything installed.
NOTE: Don't modify the registry if you don't know what you're doing. :)
You can download the registry file here.
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