Most likely, this has occurred because you have installed Office with that product key on 3 different PCs (even if not at the same time) or have had to reinstall it on an existing PC after making a hardware change. In such cases, telephone activation may be required.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thank you for your reply.
When i wanted to active my office 2010 home and business through thelephone(whit skype) it gave me a message: The installation id entered was not valid.
Thank you