We have a Click Once installation package that utilizes SQL Server 2008 R2 Express. It sets up an instance called SQLEXPRESS_2008.
When I run the setup.exe I am immediately presented with this error message:
"A prerequisite failed for Package "SQL Server 2008 R2 Express With Tools"
Package failed with message "SQL Server 2008 R2 Express (x64) cannot upgrade the existing instance of SQL Server 2008 Express (x64 WoW) named 'SQLEXPRESS_ASL'. Uninstall this instance of SQL Server 2005 Express and retry installing SQL Server 2008 R2 Express
(x64)."
Weird thing is that there isn't a SQL 2005 instance of SQLEXPRESS_ASL installed, but rather an instance called SQLEXPRESS.
I even tried installing the instance manually (which worked) and the failure message still appears. I have encountered this error once before, and was able to correct it by removing the SQL 2005 instance called SQLEXPRESS. In this case I cannot remove that instance as it is in use