That pesky SQL Server Express. I’m going to have to support it, it’s time to start collecting tips from the veterans….
These problems left me stranded for days, then today, on another machine, I hit a different set of problems I kept getting the following “Failed to generate user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed.” and if I set “User Instance” to false the following “An attempt to attach an auto-named database for file C:\[app_path]\ASPNetDB.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.”
If you don’t want to follow the link, the short answer is that SQLExpress creates a directory per user in “c:\Documents and Settings\[user]\Local Settings\Application Data\Microsoft\Microsoft SQL Server Data\SQLEXPRESS” that it uses to store information. Deleting this directory has fixed both of my problems.
[from Enjoy Every Sandwich]