My main laptop is in for repairs at the moment so I have dug out an old Sony Vaio to use in the meantime.
This Vaio is running Windows 8 quite happily (upgraded from the original Vista many moons ago).
I have been trying over the last couple of days to upgrade from 8 to 8.1 with no success.
I'm getting the error 0xC1900101 - 0x20017 and the Windows version is returned to 8.

I have tried updating the video drivers and although newer drivers are available at Nvidia none of them will install. The installer does not find a compatible video card (though I've been careful to choose the correct versions).
However the Nvidia site does say that any video drivers should come from the Sony site (but there aren't any according to Sony).

I've also disabled Windows firewall and Windows Defender.

I've even tried uninstalling the video card and just using the basic Microsoft Display driver but had the same result.

I've run the upgrade assistant and it reports that I have 1 thing that needs attention - namely a Texas Instruments card reader driver update, for which a link is given to download. I've downloaded and run this update.

The upgrade to 8.1 still fails in the same way.

Any ideas would be appreciated. Thanks.