[noggin]

Desktop, but does it matter ?   

  
Yes - as laptops often have one video output and it's often HDMI 1.4, whereas Desktops often have DisplayPort and HDMI 1.4 and HDMI 2.0.

Does your Windows desktop not drive your display in UHD or does it just not output HDR?

Have you installed the latest Windows 10 updates?

Do you see the HDR option?

Or are you able to get Windows to run in HDR,  but just having issues with Kodi?  

how do i know if the output is in HDR ? I set the resolution to 2160p. I don't know where in nvidia settings to enable hdr.

yes, latest win 10.

where is the hdr option in win 10 ? 

Settings->Display->Windows HD Colour settings I think.