Follow these steps:

1. Close all Microsoft Office applications.
   
   
2. Click Start, click Run, type regedit in the Open box, and then click OK.
   
   
3. Locate the following registry subkey:
   HKEY_LOCAL_MACHINE\Software\Microsoft\Office\12.0\Registration
   
   Note You may also find another subkey that resembles the following subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0\Registration\{91120000-0011-0000-0000-0000000FF1CE}
   
   
4. If you find additional subkeys that reference Microsoft 12.0 registration, open each subkey, and then identify the product by the ProductName entry.
   For example: ProductName=Microsoft Office Professional Plus 2007
   
   
5. When you find the subkey for the product from which you want to remove the existing product license key, delete the following entries:
   • DigitalProductID
   • ProductID
     
     
6. Exit Registry Editor.

The next time that you try to run an Office application, you will be prompted for a new product license key. Then, you can enter the product license key.

7 Hit the "Install Now" button and you Office app, will be updated with the new key. After updating you can activate you Office app, without reinstalling it.