When you drop the default database of the farm Service Account…
by liquidpooled on Nov.14, 2008, under Microsoft, Office, SQL Server 2005, Sharepoint Server, Windows SharePoint Services
When cleaning up a number of older databases in a QA/Staging environment (databases dating back to 2003), we managed to delete the default database for the SharePoint database system account. After deleting the database, the user will longer be able to perform actions on the SQL instance (login, view databases, etc.) when logging on through Management Studio. To fix this error, log on to your SQL server as another administrative user (like the “sa” account), and execute the following:
sp_defaultdb 'SQLSERVER\dbuser', <DEFAULT DB>
Replacing