Thanks Dieter "Fernando" for welcoming me and good answer to my NVMe question.
Well its a driver question, I have inserted a WD-Black SN 850, the BIOS at Z170M-Plus recognise SN850, but Win7 do not recognize since I do not have a proper driver.
Then I found your great page about NVMe drivers and I thought to insert a Samsung instead with Samsung driver you recommended.
1. insert Samsung 980 PRO instead as second drive
2. install driver in Win7 >>Samsung NVMe Driver Installer Set v3.3.0.2003 for Win7-10<< you mentioned at first page
3. when Win7 found 980 PRO then I use boot diskmanager and clone my Win7 SSD 500GB to new 980 PRO 500GB
4. take away SSD and make new 980 PRO active boot disk
5. viola, I have a much faster C: drive with Win7 :)

But as you wrote, clone maybe do not work, so I must make a clean install with install.wim of the Win7 ISO file with integrated MS NVMe Hotfix(es)

Regards Lasse (alias laser)