While service accounts generally don't require user profiles to be associated with them, there is at least one exception I can think of (you might be able to think of others) and this is when you need to pass a user environment variable to a service running on your server. Now normally you create user profiles by logging on with a user account, but you don't want to log on to your server using a service account just to create a profile for that service. Instead, you can create a user profile *without* logging on with your service account. To learn how to do this, see the KB article titled Programmatically Cause the Creation of a User's Profile found at http://support.microsoft.com/default.aspx?scid=kb;en-us;196070.
Mitch Tulloch is lead author for the Windows Vista Resource Kit from Microsoft Press, which is THE book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. Mitch is also the author of Introducing Windows Server 2008, the first book from Microsoft Press about the exciting new server platform. For more information on these and other books written by Mitch, see www.mtit.com.