I have tried many of the online recommendations for fixing this, and none have worked.
Time has passed since many of those posts were written, and i'm hoping that (maybe) some deeper insight into the problem has come along since then.
I'm particularly curious about the errors in CBS.log reported by sfc:
Cannot repair member file ... settings.ini
... there was a similar problem with another file, but I fixed that one by copying the original version of the file from the (Acer laptop) hidden partition into the winsxs directory.
But that approach does not work for settings.ini.
By deleting settings.ini in users-myUser-appdata-etc-w
ebar, a new settings.ini appeared, and the sidebar suddenly came back from wherever it had gone. But the new settings.ini still does not match the settings.ini in the windows-sxs folder, even after reboot.
So sfc still complains that settings.ini cannot be fixed.
And it looks like writing to that folder (ie copying in the settings.ini that will match) is highly forbidden and can't be done.
And it doesn't work to copy the window-sxs settings.ini into users-appdata ... sfc still fails, and then users-appdata settings.ini gets replaced on reboot.
So two questions:
1) Is there a trick to getting the window-sxs settings.ini to update, and thereby match the one that vista puts into users-appdata?
2) Is it known that error 80070490 will always occur
if sfc finds system files it can't fix?
In other words, is it pointless to try anything else until sfc comes up clean?
I had planned to try the clean boot method next, to look for funky startup services, but don't want to waste any more time on this if the settings.ini situation makes it hopeless.