WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
1. Close all Office programs.
2. Click Start, click Run, type regedit, and then click OK.
3. Locate and then click the following subkey, depending on your version of Windows and of Office:
2007 Office system
2007 Office system
4. Export the Registration subkey.
You can make a backup of the values under the Registration subkey if the new product key does not work. To do this, follow these steps:
1. Right-click the Registration subkey, and then click Export.
2. In the Save in list, select a location to save the registration entries.
3. In the File name box, type a name for the .reg file that you want to export, and then click Save.
Note In steps 4a through 4c, you created a backup of the Registration subkey. You can restore the Registry settings of the Registration subkey by double-clicking the .reg file that you saved in step 4c. The contents of the .reg file are automatically exported to the Registry.
5. Under the Registration subkey, there may be several Globally Unique Identifiers (GUID) that contain a combination of alphanumeric characters. Each GUID is specific to a program that is installed on your computer.
Click a GUID. Then, view the version of Office that is listed in the right pane for the Productname registry entry. After you find the GUID that contains the version of your Office program, follow these steps:
1. Delete the DigitalProductID registry entry.
2. Delete the ProductID registry entry.
6. Close Registry Editor.
7. Open an Office program, such as Microsoft Word. When you receive a message that prompts you for the product key, type the correct product key, and then click OK.
Note: The steps to change the resistration key for Office 2003 and XP are the same except for step 3: