windows 8 product key has lost. this genuine piece. I want revive my system to keep updated
What do you mean by it is lost?
"Windows 10 Embedded Product Key Tool"
https://neosmart.net/blog/2014/windows-10-embedded-product-key-tool/
"We’re proud to introduce the immediate release of our newest utility for Windows users: the NeoSmart Technologies Embedded Product Key Tool. Designed for users of Windows 7, Windows 8, and Windows 10, our embedded product key tool will retrieve and display the Windows setup product key embedded in the BIOS or EFI, allowing you to store it for safe-keeping or use it to reinstall Windows with an official Windows setup image."
You can also use:
"Belarc Advisor - Free Personal PC Audit (Version 8.5c)"
http://www.belarc.com/free\_download.html
Or:
"Product KeyFinder"