Compatibility issues stand in the way of installing Windows 10 May 2019 Update on some Macs
Some Mac users -- who, thanks to Boot Camp, are running Windows 10 on their Apple machine -- are encountering a problem upgrading to Windows 10 May 2019 Update (version 1903).
A compatibility issue with the Mac HAL Driver (machaldriver.sys) is blocking the installation. The problem remains more than two months after the May 2019 Update was released, and Microsoft is still working away on a solution.
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The issue is affecting people trying to install the May 2019 Update on an older Mac (which mean anything from before 2012), as well as anyone with older versions of Apple Boot Camp or Windows Support Software drivers installed.
The following error message appears:
Mac HAL Driver - machaldriver.sys: Your PC has a driver or service that isn't ready for this version of Windows 10.
In a support article about the issue, Microsoft said:
Mac devices prior to 2012 or newer Mac devices with the older Apple Boot Camp or Windows Support Software drivers have a compatibilty hold in place and are unable to update to Windows 10, version 1903. Specifically, devices with MacHALDriver.sys dated September 24, 2011 01:57:09 or older in Windows\system32\drivers are affected.
If you're lucky, you will find that the simply updating Apple Boot Camp Windows Support Software drivers will be enough to allow the installation to proceed (just check for update in the App Store). If not, you'll just have to wait until later this month when Microsoft is due to release a fix of its own.