So, I had Office 2010 installed on my PC. Then for some problems with other programs, I had to format my PC. Then, I opened Microsoft Office 2010 to reinstall it, then I inserted the product key I've written on a sheet, and it gave me error: the product key doesn't exist. So I tried using WindowsKeyFinder, which found another product key - that one didn't work neither. What might the problems be? Thanks for anyone who will answer this question.

Hi,

Please first make sure whether you've inserted the correct product key. For how to find your Product Key for Office 2010, please refer to this article: https://support.office.com/en-ca/article/Find-your-Product-Key-for-Office-2010-1e8ef39c-2bd4-4581-a0ae-5cf25ebed489

Also, have you ever made changes to your hardware? If your hardware is substantially different, then it will be considered as a new computer. If this is the case, you might need to activate your Office 2010 via telephone.

If issue persists, I would suggest you contact Microsoft Custom Service directly for further assistance: http://support.microsoft.com/en-us/gp/customer-service-phone-numbers

Hope this helps.

Regards,

Ethan Hua
TechNet Community Support