You may need to alter or change Microsoft Office 2007 (aka 2007 Microsoft Office System programs and suites) product license key or volume license key (VLK) which also known as serial number or CD key. You can modify or change product key for 2007 Microsoft Office programs or suites by first uninstall or remove Microsoft Office and then reinstalling the business productivity suite. However, you can follow the following steps in order to reset and change the Microsoft Office 2007 product serial key without the need to uninstall or reinstall 2007 Office system suites.

Note: The following steps involve modification of registry key values, which may corrupt your Windows if done incorrectly. Backup registry first before performing the workaround.

1. Close all Microsoft Office programs.
2. Click on Start button, then click on Run.
3. Type “regedit” (without quotes) in the Run text box, and click OK or press Enter.
4. Locate and then click the following subkey:

HKEY_LOCAL_MACHINE \Software\Microsoft\Office\12.0\Registration

Inside, you will find another subkey that resembles the following subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0\Registration\{30120000-0011-0000-0000-0000000FF1CE}

Tip: For user with 64-bit (x64) Windows, go to HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\12.0 instead.
5. Optional: Backup this registry branch by exporting the Registration subkey to a file, just in case the new product key does not work and you have to restore back the old product key. To export the registry, right click on the Registration subkey and click on Export, and follow the on-screen prompt to enter a file name for the registry file and choose a location to store it.
6. Under the Registration subkey, there may be several Globally Unique Identifiers (GUID) subkey that contain a combination of alphanumeric characters. Each GUID is specific to a program that is installed on your computer.

If you find additional subkeys that reference Microsoft 12.0 registration, then click and open each GUID subkey to view and identify the Office product version by the ProductName registry entry in the right pane. For example:

ProductName=Microsoft Office Professional Plus 2007
7. After you find the GUID subkey that contains your Office product or program which you want to remove the existing product license key or registration details, delete the following registry entries by right clicking on the registry entry in the GUID subkey, click Delete, and then click Yes:

• DigitalProductID
• ProductID
8. Exit Registry Editor.
9. Run or open an Office application program, such as Microsoft Word or Excel or Outlook. Office 2007 will prompt you to enter a new 25-character product key.
10. Type in the valid and genuine product key, and then click OK.
11. Then when prompted to choose your preferred type of Microsoft Office 2007 installation, press on “Install Now”.
12. Microsoft Office 2007 will be updated with new product CD key or volume license key, and ready for activation (if it’s a non-VLK serial) or use.

Note: If you’re having problem with your new Office 2007 product key, simply double click on the backup registry .reg file created at the optional step above to restore the registry settings of the Registration subkey so that the original value can be imported back to the registry

Microsoft Office Licensing Reference Guide