In order to clone Windows Server 2003 system a to different machine, you should first prepare Windows using Microsoft System Preparation Tool (sysprep). According to Microsoft Knowledge Base Article - 298491, "One problem from duplicating an installation of Windows 2003 is that each cloned computer has the same security identifier (SID) and computer name. This may prevent the cloned computers from functioning correctly in a workgroup or a domain. To work around this problem, administrators use the System Preparation Tool (Sysprep.exe) to remove configuration settings that are unique to the computer such as the computer name and SID. The resulting image can then be safely reused for installation on other computers." This issue also exists in Windows NT 4.0 and Windows XP, therefore computers running those operating systems must be prepared as well.
Here come the most important question - if there is dissimilar hardware, then the target system will not boot after cloning. To transfer a Windows Server 2003 system to a machine with dissimilar hardware, you will need to use EaseUS Todo Backup Server.
You can clone Windows Server 2003 operating system to different hardware according to the following steps. Windows Server 2012/2008 and Windows 8/XP/Vista/7 also supported.
Step-by-step tutorial: How to clone Server 2003 to different hardware?
Free Download EaseUS Todo Backup Server to have a try.