Microsoft Office 2007: "This copy of Microsoft Office is not genuine"

Some time ago Microsoft published an Update named "Office Genuine Advantage (KB949810)".
This update causes some Versions to display a message like the one below:

This copy of Microsoft Office is not genuine.


Please excuse this interruption. This copy of Microsoft Office did not pass validation. Click Learn More for details and for help identifying the best way to get genuine Microsoft Office.

When your Office shows a message like this it means that the version you are using is indexed by MS as stolen or unauthorized copied.
Of course there exist several reasons why this could happen; either someone copied your serial and published it in some strange forums, or you have bought your PC with MS Office pre-installed and the first owner still uses its version, or you simply downloaded it from somewhere.

There exists a very simple solution to come over this problem, and if you have not stolen your copy feel free to use this solution in order to remove this annoying pup-up.

1. Close Office completely
2. Go to C:\windows\system32
3. Locate the following three files:
   OGAAddin.dll
   OGACheckControl.dll
   OGAEXEC.exe
4. Rename all of them into *.old to obtain
   OGAAddin.dll.old
   OGACheckControl.dll.old
   OGAEXEC.exe.old
5. Re-run Office
6. (delete the *.old files)

Now the pop-up doesn't show up again and you can use your copy as before the update