Windows 2003 Server has expired and there is no more support for the server. But the problem is still some of the organizations are using Windows 2003 as their servers such as active directory, file server, dhcp server.
To migrate some server roles are very easy because those have some inbuilt features or tools to migrate server role to new version. Also for some servers we can do the in place upgrade to new version. Windows 2003 we can upgrade to Windows 2008 R2 and then we can upgrade to the Server 2012. All the upgradable versions are listed in the below tabl
VMware,Microsoft Knowledge Sharing Portal 