How to reset Product Key - Microsoft Office

Today i got problem with ms office, cannot activate because it said already reach the limit for the product key. Actually i don't know which installation cd have been used.

I must install new ms office to get new product key but anyway i don't know which cd already used and validate. After searching in the internet , i got solution and i tried , successful.

This is the step :

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\{30120000-00
5. 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
   
6. Exit Registry Editor.
7. Run or open an Office application program, such as Microsoft Word or Excel or Outlook. Office will prompt you to enter a new 25-character product key.