With Windows Server 2008, Microsoft introduces a new set of certification options. In the prior versions of Windows server, the Microsoft Certified Systems Administrator (MCSA) and Microsoft Certified Systems Engineer (MCSE) certifications have been pretty standard. The certification path has changes for Windows Server 2008and following are the steps to upgrade.
Windows Server 2008 is a next-generation server operating system that helps IT maximize control over its infrastructure, while providing unprecedented availability and management that leads to a significantly more secure, reliable, and robust server environment.
People Certified with MCSA and MCSE on Windows Server 2003 should consider taking the appropriate upgrade test to make the immediate transition to Windows Server 2008.For the MCSA, the test is 70-648; for the MCSE, the test is 70-649.These tests will be used as a bridge form MCSE/MCSA 2003 to MCTS: Windows Server 2008 Certifications.
Exam 70-649 is for IT professionals who currently hold an MCSE on Windows Server 2003certification and work in medium to large companies. The MCSE on Windows Server 2003 is a prerequisite for this exam. Exam 70-648 is for IT professionals who currently hold an MCSA on Windows Server 2003 certification and work in medium to large companies. The MCSA on Windows Server 2003 is a prerequisite for this exam.

Source: Microsoft
