When you first install a Microsoft Office product, such as Microsoft Office 2007 Home and Student edition, you must register it with a unique product key before you have access to the full features of the program. If you need to change the product key for your Office 2007 Home and Student installation, you can do so by removing the saved registry value that contains the old key then re-registering it with the new product key.
Close any open Microsoft Office programs on your computer.
Press the "Windows" key and "R" key simultaneously. The Windows Run application will appear.
Input "regedit" into the Run window and press "Enter."
Navigate to the following registry subkey, using the navigation pathways in the left window pane:
Right-click on the subkey in the left window pane and select "Export." A Save file window will appear. Navigate to your computer desktop, input "ProductKeyBackup" as the file name and click on "Save." This backs up the product key registry value for Office 2007 in case problems arise.
Expand the "Registration" subkey in the left window pane. A list of Globally Unique Identifiers (GUID) will appear. GUIDs are a random string of alphanumeric characters.
Click on each of the GUIDs and locate one that has "Microsoft Office Home and Student Edition 2007" set as the "Productname" registry value in the right window pane.
Right-click the "DigitalProductID" registry entry in the right window pane and select "Delete." Click on "Yes" to confirm the delete.
Right-click the "ProductID" registry entry in the right window pane and select "Delete." Click on "Yes" to confirm the delete.
Click on "File" and select "Exit" to close the Registry Editor.
Launch any Microsoft Office 2007 Home and Student program on your computer. A message will appear that asks for a product key. Input the new product key and click "OK."