If you have configured the user database any of below feature of SQL Server 2008 Enterprise Edition
— Data Compression
— Transparent Data Encryption
— Change Data Capture
Above list of features will internally change the way the database engine stores information within the database files. If a database configured to use any of the above features which are specifically designed to be used in Enterprise Edition of SQL Server 2008, it cannot be moved to other editions of SQL Server 2008.
You can check the above feature by querying the sys.dm_db_persisted_sku_features DMV against database.
SELECT feature_name FROM sys.dm_db_persisted_sku_features ; GO