Hello. My name is***** will be providing an answer to your question today
Thank you very much for giving us an opportunity to help you. If you like I can log on to your machine and help you.
If you have not made any hardware changes to the computer, you can re-install the Office using the same product key.
In case you have made changes to the hardware of the computer, then during activation, it will be considered as a new computer. In such cases, you may choose the phone activation and activate the Office.Here the info https://support.microsoft.com/en-us/kb/326851 Waiting your feedback