Office retail licenses could... up until 2013 ... be moved from computer to computer.
Apparently...not any more. Check out the 2013 retail EULA:
Office 2013 Software License Agreement - Office Watch:
Under our license we grant you the right to install and run that one
copy on one computer (the licensed computer) for use by one person at a
time, but only if you comply with all the terms of this agreement. Our
software license is permanently assigned to the licensed computer
You may not transfer the software to another computer or user.