what is the proper / quickest way to report a key stolen? and prevent it from any "future" happenings.

Hi,You should call Microsoft Hotline.If you stick the product key to the back of your laptop or on the side of your desktop computer. Victor Constantinescu - MVP Security, MCTS

Hi harrycomet, you can visit the following link to submit a support incident regarding the key issue: https://support.microsoft.com/oas/default.aspx?LN=en-us&iid=224026&iguid=e5ea4c44-9489-4d8f-b372-dbfc6ee4e99e_2_3&x=21&y=15 Hope this helps!Sean Zhu - MSFT