Mainstream support for SMS 2003 will end on January 12th, 2010. On January 12, 2010, SMS 2003 will be entering the extended phase of support.
What is the difference between Mainstream Support, Extended Support, and online self-help support?
Note: A hotfix is a modification to the commercially available Microsoft product software code to address specific critical problems. For details, see http://support.microsoft.com/gp/lifepolicy and the Lifecycle calendar for SMS 2003
See the Configuration Manager Upgrade and Interoperability Planning and Deployment documentation for help on planning your upgrade to System Center Configuration Manager 2007.