If you are trying to Update to Windows 10, version 1903 on Apple Mac devices released before 2012 or newer Mac devices with older versions Apple Boot Camp or Windows Support Software drivers installed then you may face inconveniences. Microsoft has blocked Windows 10 newer update 1903 to operate on them.
The support page of Microsoft clearly addresses the issue and mentions the cause as well as the solution to the issues. This cannot be tracked easily since the web crawlers have been prevented to index the text itself that prevents finding the support page simply by the search. Microsoft has addressed that Windows 10 May 2019 Update may fail to install on old Mac, causing inconveniences, purely due to a compatibility issue.
The inconveniences include an Update compatibility hold followed by a message :
“Mac HAL Driver – machaldriver.sys: Your PC has a driver or service that isn’t ready for this version of Windows 10”.
The system may unexpectedly break or generate glitches in case if other unverified parameters are used to force the installation. An error message might also pop up to resist the action if not done after the proper technical examination.
The reason stated by Microsoft is that Mac devices prior to 2012 or newer Mac devices with the older Apple Boot Camp or Windows Support Software drivers have a “compatibility hold” in place that does not make the update possible into the system.
HAL is a Hardware Abstraction Layer, which is code that sits between hardware drivers — like those for audio — and applications. Effectively, this acts as an interface between Windows apps and the Mac hardware.
Naming Specifically, devices with MacHALDriver.sys dated September 24, 2011, 01:57:09 or older in Windows\system32\drivers, Microsoft states that the new update of 1903 can neither be downloaded nor can it be installed.
If you are wondering on how to get the 1903 update on your Mac despite the fact that it is system incompatible, you may try with updating your Apple Boot Camp Windows Support Software drivers. You may just find the updated Windows support software, in macOS, choose Apple menu > App Store, then install all the available updates as per your eligibility for them. Another Alternative is to try making your way through the suggestions made in the Support Article by Apple to manually install the update.
Though there is no direct solution available for the above-mentioned issue, Microsoft has promised to come up with a possible solution by the end of July.