If Changing Office 2007 CD is needed, it can be done by removing two registry keys.
1. Open registry editor (Start<Run<Regedit).
2. Browse to : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0\Registration
3. Usually there is one data value under "Registration". Search for DigitalProductID and ProductID and
4. Open any office application and insert the new product key.