That won't work. However, if you can find someone with the same version of Office has a CD, you can install using their media and your product key. (this doesn't violate your license)
You might hunt around on the system and see if they had the Office bits stashed in a folder somewhere. That's common in medialess systems.
Sometimes the OEM would have media that they would sell you for a good price, and sometimes there's a System Restore kit you can buy.
Jim.