Feature Update 1803
Not really expecting the Feature Update, it dropped on me last Friday. This was a Tower system with an Intel SSD for system boot.
Whatever the update did - the boot disk was unusable. No system checkpoint or rollback available.
None of the normal Windows tools, like chkdsk or fixboot helped. Windows ISO download did not help.
Interestingly enough, Acronis True Image had no trouble reading the disk. Something in 1803 is not compatible with the boot device.
Gave up trying to fix the problem, so I used the Windows 10 ISO to reinstall Windows. Would not activate; could not find the digital license. Microsoft wants me to buy a new license for the system they broke. This was a Vista system originally, with a paid upgrade to Windows 8, and a free upgrade to Windows 10 from there. In theory - I could reinstall Vista and do the upgrades again - but Microsoft no longer offers the free Windows 10 upgrade. And Microsoft wonders why people hate them...