How do I configure my SQL Server instance to use a different Edition with minimal side effects?
You could possibly follow these steps to &quot;migrate&quot; the databases to a &quot;new&quot; SQL Server 20xx instance.

detach the databases in the running SQL Server Express instance and leave them where they are.
Script out any logins that you require.
Don't delete/drop any databases.
De-install the SQL Server 2008 R2 Express Edition.
Install the SQL Server 20xx Standard Edition. (you can even use the instance name SQLEXPRESS; how clever is that?)
Add the SQL Server Logins to your &quot;new&quot; SQL Server 20xx Standard Edition instance.
Once the &quot;new&quot; SQL Server 20xx Standard Edition is running attach the &quot;old&quot; databases to your new SQL Server 20xx instance.
Change the database compatibility level to 110 (if required).

Enjoy a &quot;new&quot; SQL Server 20xx Standard Edition instance hosting your &quot;old&quot; databases.