Hello Suna Ozmen,
The Product Key (found on the sticker on the side or bottom of your computer) is for Windows only and will not work for Office.
Full Versions of Office do not, normally, come standard on computers. Computer Manufacturers will often include a Trial version of Office, which allows you to use it for a limited time, but if you wish to continue using it, you would need to by a Full Version of Office.
If the copy of Office, that came with your computer, is supposed to be a Full Version, then the Product key would be included in the documentation that came with the computer. If you are unable to find the Office Product Key and you still believe that the computer should have come with a Full Version of Office, please contact the Person, Company, and/or the Computer Manufacturer, that you bought the computer from, for further assistance.
Thank you,
Darin Smith
WGA Forum Manager