Have you installed the Galactic database yet from the downloaded source code for the book? If not, run the 'Create Galactic Database.sql' script in the 'Galactic Database Install' folder. At the bottom of the script is the userid and password:
exec sp_addlogin N'GalacticReporting', N'gds', @logindb, @loginlang
In order to set up the data source, you must use this userid and password (unless you change it to something more convenient). See if that works for you and hollar if it doesn't.