After a few failures to upgrade to 8.1 with these errors
0xC1900101 - 0x40017
0xC1900101 - 0x30018
0xC1900101 - 0x20017
With a retina MacBook Pro 10,1
I decided it might be connected to my Windows 8 installation being EFI boot so I decided to scrap that and return to a Bootcamp partition.When EFI booting Windows on my machine it is necessary to remove the Intel video driver (long story) so only the Nvidia GT650M is usable.
As my problems upgrading to 8.1 seemed to be graphics driver related I tried to update to the later drivers from Nvidia but during removal of the driver already in use the screen just went black and the system just got stuck there - whatever I did I couldn't proceed. Neither would the system reboot to a desktop - just a flashing black/grey screen. I'm sure I tried every method possible but still no good.
Anyway I fixed it up a couple of times and decided to try it in safe mode. Also no good .
As soon as the driver was removed the system stopped recognising that the Nvidia card was present and therefore the Nvidia installer could not proceed with installation
So I decided to re-install Windows 8 in a shiny new Bootcamp partition.
Once installed I ran all the updates and tried again to update to new Nvidia drivers.
Same story as before
I eventually got the old driver out and the new 327 driver installed in safe mode and it rebooted successfully to a desktop
Once that was ok I disabled the Windows Firewall and Defender's real-time protection then downloaded the upgrade and ran it. It ran ok and after 8 reboots (I think it was) it booted successfully
So, it's installed and running quite nicely
It seems quite good actually