On Friday, April 6, 2018 at 10:08:47 PM UTC+8, Paul wrote:

Do you have an exact copy of the error message ?
You could try popping that into Google and see
what others have run into.


Well, I didn't find the answer with Google, but Bing dug up an obscure
geek's blog. It seems Windows update didn't just look in the registry, but
scanned the whole disk and finds a DLL belonging to an old malware scanner,
which is enough to cause it to hold its breath.
Now when my missus got this PC years ago, she copied the entire C drive of
her old WinXP PC onto a directory in the new PC so she could access her old
files. And that old PC had Avira installed.