how to dual-run Office XP/2K3 and Office 2007

To run both versions of Office 2002/3 and Office 2007 on same machine:

  1. Set the file-types to open with relative version of Office: .doc, .docx, etc.
    (i.e. set .doc to open with word 2002 and .docx with 2007)
  2. Open Regedit
  3. HKEY_CURRENT_USER\Software\Microsoft\Office

For Word 2007:

  1. \12.0\Word\Options
  2. create a new DWORD value and set it to 1

For Word 2003:

  1. \11.0\Word\Options
  2. create a new DWORD value and set it to 1

For Word XP/2002:

  1. \10.0\Word\Options
  2. create a new DWORD value and set it to 1

Credits to: Geoff
http://www.gearfire.net/run-office-xp-office-2007-computer/