Attach SQL Server 2008 R2 on SQL Server Express 2008 I have a database on SQL Server 2008 R2.

I want to attach it on a SQL Server Express 2008 instance running on Windows 2003.

I set the SQL server compatibility level on the database to SQL Server 2005 in SQL Server 2008 R2 Management Studio before detaching.

But I can't attach this database to my SQL 2008 instance running on Windows 2003 due to a "compatibility error".

How can I get around this?
You can't attach a SQL Server 2008 R2 database to a SQL Server 2008 or 2005 instance. You can only go up, not down; you can't make your 2008 R2 database compatible with previous versions. The solution is to remove your Express instance and replace it with a 2008 R2 instance, then you will be able to attach your database...