Volume licenced copy of MS Office 2007 shows “Non Commercial Use” in title bar

I have just removed the demo copy of Office 2007 preinstalled on a new laptop and replaced it with an install of the full professional edition downloaded from the MS Volume Licensing site and installed one of our volume licence keys, yet the apps (Word etc.) show "Non Commercial Use" in the title bar, which is what usually happens in the Home and Student edition.

I have tried:

• Deleting the Office registration keys
  in the registry and using one of our
  other Office 2007 volume licence keys
  (we have 7) when prompted to re-register

• Uninstalling Office completely and
  reinstalling it from a
  newly-downloaded ISO burned to CD and
  also from a compressed file that installs
  from hard disk/USB stick (both from
  Microsoft – no dodgy stuff)

Yet the non-commercial message persists. Although it's a cosmetic issue, the laptop is going to be used for customer presentations and so the sales person is rightly concerned about the image this portrays.

I presume there may be something floating around the registry or in a file somewhere but I can't find it. Articles I have found elsewhere just refer to the message being related to the use of a Home and Student licence key, which is 100% not the case.

Any thoughts? Thanks.