Determine whether computer includes Windows 10 upgrade rights

[KD50501]

I work for a company that manages hundreds of desktop computers for many companies. We're beginning the push to get all of our users up to Windows 10 since Windows 7 is reaching end of life in January. I'm quite certain that many of the computers we manage, which are currently running Windows 7, came with Windows 10 upgrade rights and a product key which is valid for either Windows 7 or Windows 10. However, I'm struggling to find a reliable way to determine whether any individual computer has a valid Windows 10 key. In most cases, we don't have the original box or receipt or any documentation that came with the computer. I have serial numbers, etc., but I need a reliable method of knowing whether a computer can be upgraded to Windows 10 without having to purchase a new license. I don't want to charge a customer for travel time and onsite labor to upgrade their computer, and then find out the product key in BIOS is only valid for Windows 7. Most computers in recent years don't come with a COA or any external indication whether it includes a Windows 10 license. Any advice would be greatly appreciated.

[banhien]

@KD50501 

I know following software can do the job but they take time to run (2 to 5 minutes to install and run on EACH computer - of course you can do 10 or more concurrently using downloaded file on USB key):

           http://www.belarc.com/free_download.html

           https://www.magicaljellybean.com/keyfinder/

The second software is much faster and simpler

Regards.