Windows Server 2003 PC replacement assistance requested.

I am a newbie to the Windows Server environment. My client has order a replacement for their old Windows Server PC. What is the easiest way for me to move the system from the old PC to the New PC. The old PC is running Windows Server 2003 SP1. The new PC is empty of software. We do have a version of Windows 2003 R2 from MS. I hoping to get advice on how to do the move to the new hardware.
Thank you
Russ