If you are already working on earning your MCSA certification then upgrading your MCSA to Windows 2008 is critical. Find out how to upgrade your MCSA 2003 to Windows 2008 right here.
If you are a Microsoft Certified Systems Administrator (MCSA) or a Microsoft Certified Systems Engineer (MCSE) on Windows Server 2003, you can upgrade your certification to earn the Microsoft Certified Technology Specialist (MCTS) certifications or Microsoft Certified IT Professional (MCITP) credentials on Windows Server 2008. Find out how to upgrade your MCSE and MCSE to Windows 2008 right here