SGX

I don't have personal experience with your situation, so can only go by the specifications. So I cannot tell you with absolute certainty that changing to Windows 8.1 will allow you to play those disks.

Your board's UEFI, in the Advanced, CPU Configuration screen, has an option called SW Guard Extensions (SGX). I cannot tell from the manual if that option is enabled by default or not. Check that this option is set to Enabled before you try using Windows 8.1.

You could also ask about this in Intel's support forum, the Chipset sub-forum is probably the best choice:

https://communities.intel.com/community/tech/chipsets

bits2000 wrote: When trying to play Ultra DVDs through Powerdvd 17 Ultra, it says: This media cannot be played because the required Intel SGX (SW Guard Extensions) wasn't started. Please reinstall the full set of Intel Management Engine (ME) software components. Error code 21204 I have it enabled in the bios. I did go to Intel's web site and downloaded the current version. Is there any thing else I can do to make it work, or start? Using the onboard graphic card which is supposed to play Ultra 4k. Z270 Gaming i7 motherboard Kaby Lake processor. Thanks

I'm not 100% certain the following applies to your situation, but this is from your board's specs:

Due to chipset limitation, the Blu-ray playback of Intel^® HD Graphics is only supported under Windows^® 8 / 8 64-bit / 7 / 7 64-bit.

http://www.asrock.com/MB/Intel/Fatal1ty%20Z270%20Professional%20Gaming%20i7/index.asp#Specification

Are you using Windows 10?

Intel does not provide the IME software from their download pages anymore for mother boards made by other manufactures, like ASRock. The IME software on your board's download page is the best version to use. But you may be stuck with the limitation I listed above.

Otherwise, do you have the Intel graphics driver installed?