Firstly, you need to know the installation path of office, such as
C:\Program Files\Microsoft Office\Office14
Run cmd with administrator privileges
Entry code, and press Enter key
cd "C:\Program Files\Microsoft Office\Office14"
Enter the Office14, and entry code.
cscript ospp.vbs /dstatus
Get the last 5 number of product key.
Then entry the follow code to uninstall the product key.
cscript ospp.vbs /unpkey:xxxxx