Just wanted to add - (in case you are real newbie like me) that the following SQL query worked for me:
Just go to either Review or Genre in the database explorer, right click on either and chose "show table data". In the "SQL pane" I added the following (please correct this to fit your database location on your own computer).
ALTER AUTHORIZATION ON DATABASE ::[C:\Documents and Settings\Allan\Dokumenter\Visual Studio 2008\WebSites\MinWebsite\App_Data\PlanetWrox.mdf] TO [sa];
And then just press the "Execute SQL statement".
