I've previously in my setup installed SQL Server Express 2005. Now I've switched to SQL Server Express 2008. I updated the command line parameters to those documented for the latter. If the comp already has SQL Server Express 2008 installed, my installer should create a new instance.

The command line parameters are as follows:

/ACTION=Install /FEATURES=SQLEngine /QS /INSTANCENAME=ABCD /SECURITYMODE=SQL /SAPWD=CunningPassword

The requested instance name does not exist on the target machine. This will end in an error -2068643838. The logs show the following error:

"No features were installed during the setup execution. The requested features may already be installed."

If I remove the /QS parameter and try to install interactively, I'll get as far as the Feature Selection page. The UI shows three options, Instance Features, Shared Features and Redistributable Features. Whatever I select, clicking Next results in the same error (There are validation errors on this page).

Any ideas anyone?