Another frequently asked question by many customers. A good answer can be found in the "Threats and Countermeasures: Security Settings in Windows Server 2003 and Windows XP" document which can be downloaded here. A little out of date (being based on WS2003 RTM and XP SP1), but dead useful information none the less.It does however contain a lot of useful security advice as well though.

If that doesn't do it for you, you can also find similar information in the "Windows Server 2003 System Services Reference" here.