Windows 10 Update Error 0x80070001

Wed, 02 Jan 2019 10:00:00 +0000

I had two Windows 10 machines which had stopped pulling upgrades from Microsoft for quite long (1703, anyone?) and I could not get it back working.
Windows Update just showed me the error 0x80070001 and did refuse to do anything.

Tried:

Clearing Windows Update Cache
WSUS Offline Patching (installed the updates, but the normal Windows Update did not start working after that…)
Windows Update Repair Tool from Microsoft

Nothing did really work, until I stumbled upon a post by OksiQuatzel:
Culprit was the installed ImDisk, a virtual Floppy Drive. With this installed and an A Drive mounted - this error arose.
As soon as I unmounted the drive and removed the driver - everything started working again.
Kind of nuts that something like this could occur.

IMdisk on Nico Maas

Windows 10 Update Error 0x80070001