How to Read Windows 8 BIOS Key from Windows 7

I have a couple of PC's that were ordered with windows 7 Pro Preloaded. They came with a WIndows 8.1 System Disk (Dell).
I would like to read the BIOS embedded Windows 8.1 Key.

All of the ones that work under windows 8, hang under windows 7.
I didn't find the right solution from the internet.
References:
ht tps://ww w.bleepingcom puter.com/forums/t/58

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