Going through a tutorial can already be a grind, which is why I found this issue so frustrating.
If you are using ASP.NET MVC and while attempting to store data (say for a login) you get:
"Your SQL Server Installation is either corrupt or has been tampered with (SQL Server User Instance only supported on SQL Server Express SKU). Please uninstall then re-run setup to correct this problem"
Though you are sure you have LocalDB installed, if possible try connecting to the localDB (via Management Studio or Management Studio Express) and disabling user instances on the localdb instance:
sp_configure 'user instances enabled','0' --Disable User Instances
If that doesn't work you may need to drop and recreate the localdb instance (obviously any data there will be lost)
You can administer LocalDb using a command line utility called, sqllocaldb:
sqllocaldb delete [instance name] sqllocaldb create [instance name]
The instance name should match the "Data Source" property in the connection string of your web.config
in your solution.
sqlexpress user instances:
For a more general discussion about the differences between LocalDB, SQL Server Express User Instances, and SQL Compact Edition