After 14th July 2015 Microsoft will no longer support any version of Windows Server 2003
If you are still running Windows Server 2003 in any form including as part of Small Business Server 2003 you need to take steps now to plan and execute a migration to a modern platform.
What does end of support mean for you?
When the extended support period concludes on 14th July systems running Windows Server 2003 fall into a non-supported mode, meaning there are no further security fixes, there is no incident support available from Microsoft, and equally important, servers used in environments requiring regulatory compliance may find it impossible to meet regulatory requirements, leading to an out-of-compliance condition.
Will your applications be compatible?
Windows Server 2012 R2 offers relatively good application compatibility with Windows Server 2003. Although Windows Server 2012 R2 is delivered as a 64-bit operating system, most 32-bit applications that have no 16-bit code segments should install and run on Windows Server 2012 R2.
What benefit is there to upgrading?
Windows Server 2012 R2 offers a lengthy list of improvements compared with Windows Server 2003, including integrated virtualization, better security, extensive scalability, new operational roles and far more. While it is a substantial learning curve to move directly from Windows Server 2003 to Windows Server 2012 R2, customers are well advised to not make an interim upgrade to Windows Server 2008 as that product is facing end of mainstream support in January 2015.