How to change microsoft office 2007 product key after installation

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Close all Microsoft Office applications.

Click Start, click Run, type regedit in the Open box, and then click OK.

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}

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

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
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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.