Why is Exchange 5.5/2000 and SQL 7.0 not supported on Windows Server 2003?
With Microsoft’s commitment to Trustworthy Computing, many changes were made within the operating system. In fact, 350 changes that affected Exchange Server were made over the previous OS. Due to the extensive changes within Windows Server 2003, to make it the most secure OS Microsoft has released so far, many legacy applications would have required vast redevelopment to be supported.