HOWTO fix Windows Update error 0x80070643

I encountered this error on several Windows 10 PCs and after a week of investigations, I discovered the problem.

This error is reported when the recovery partition in your system disk is too small.

The solution

The solution is to resize it to 900 Mb, or even better to 1 Gb.

A task that usually involves two sibling partitions, and that requires a good amount of prudent awareness.
Usually, you have to shrink a sibling partition and add the gained free space to the recovery partition to reach the needed size.

There are many ways to do the activity, and my choice was the portable version of this awesome utility that completed the task in a few minutes.

Good luck