The default database is based on your login's default database setting on the SQL Server. For SQL Server 2005, you can set the default database by:
ALTER LOGIN <loginname>
WITH DEFAULT_DATABASE = <database>
Of course, if you're login is getting access via a Windows group, you have two options:
1) Changing the default database for everyone in that group
2) Explicitly creating a login for your user account and setting the default database (this can be done in the CREATE LOGIN statement itself)
K. Brian Kelley
@kbriankelley