I've never seen anything like you describe, and especially "installs Google toolbar" is NOT something Microsoft would be likely to do. Many update installs include a reboot, and if the current (at time of update) OS had a problem the reboot might have reverted back to an older setup from System Restore. Since Restore only keeps the last half-dozen successful changes, it would be unlikely to go back very far, but a new versions gets saved only when you restart after changes, so it's the number of restarts that counts, not the calendar.

Another possibility, assuming you've had more than one user ident on the machine, is that you've just restarted as a different user(?).

If the other machine wasn't installing updates when you shut it down, you should be able to restart it and stop installation of the latest update, at least until you're ready to shut down again.

If you can get it up, you should be able to finish a backup by exporting a copy of your shortcuts before allowing an update. Most of what you seem to have lost should be in your "username" folder, so just copying the folder to somewhere else should get most of what you lost ("should" and "will" are two different things?). If you're using a "password locker" of some kind, you may or may not be able to make a backup, since a "locker" should be encrypted and moving, copying, or making a backup of encrypted files doesn't usually work well unless you can unencrypt before copying. "Remembered" passwords are usually just cookies, and theoretically you can copy them and put them back later, although it doesn't always work as well as it might. (Cookies crumble so often I don't usually try to save them.)

Stilly reported in another thread that an "incorrect signature" caused a Microsoft AV program to foul her Chrome recently, but your description doesn't sound like that glitch was involved since the sig has been corrected, and the AV program affected wasn't one you'd be likely to use.

John