In July 2010, Microsoft ended Mainstream support for the Windows Server 2003 family and on 14th July 2015, Microsoft will end Extended support. This will mean that there will be no more updates developed for the Operating System which includes fixes for any vulnerabilities.
What does this mean?
With no fixes available, your server will be vulnerable to attack and could easily be compromised. If you work in the Payments industry, then your server will fail a compliance audit for PCI DSS. You may also find that any applications that you run on your server may not be supported by the vendor.
What can you do?
DSW can help you analyse your 2003 estate and look at what upgrade paths are available for your applications. In short, your best answer is to upgrade to Windows Server 2012 R2 and again DSW can help you to plan and implement this.