Can't disable Vardecimal Storage Format

I recently moved a database from a 'SQL Server 2005 SP1' instance to 'SQL Server 2008 SP1' (using detach - attach). I now need to move it back but it fails with the error:

The database 'MyDB' cannot be opened because it is version 655. This server supports version 612 and earlier. A downgrade path is not supported.

After a bit of research I believe this is related to the new database option 'Vardecimal Storage Format' which has somehow been set ON for all my databases. I did not set this on myself, but if I check the database options in Management Studio (2008) I can see it is set to 'True' for all my databases. Also, this particular option is disabled in the UI, so I cannot turn it off.

I then tried the following to turn it off:

exec sp_db_vardecimal_storage_format 'MyDB', 'OFF' go

which reported success, but when I check the options it is still ON.

I then read this very detailed article: "http://msdn.m开发者_Python百科icrosoft.com/en-us/library/bb508963.aspx" which states the following requirements to turn this option off:

1. Ensure no tables use vardecimal storage. Confirmed.
2. Set recovery mode to simple and do full backup. I did this.

But none of this makes any difference either. The option is still on and I can't change it.

Both instances of SQL Server are Express Edition (which isn't supposed to support Vardecimal Storage Format anyway).

Any ideas on how to turn this option off?

The vardecimal is a red herring because you can't downgrade a database whether this setting is true, false or non-existent. It's been asked before: Another question and again

Vardecimal is deprecated in SQL Server 2008 and has been replaced by compression of rows/tables.

You could try exporting your data to a script for an earlier version of sql server.