Working on my son's laptop, home from college.
I wanted to make sure it's up to date and ran windows update. said checking for updates for hours. googled, and ran a microsoft repair tool. said it found and fixed some things.
Service registration is missing or corrupt
Windows update error 0x80070490
problem installing recent updates
Rebooted, tried win update. again, overnight, didn't get past checking for updates.
ran that tool again, it found / fixed the same errors.
in the procerss I noticed that even though this is a workgroup PC / home user, it had a check box to check for updates from windows udate rather than your sys admin. I found a registry patch that got rid of that check box (and I assume it goes to windows update now).
ran the tool again, it found / fixed the same errors (so it's not really fixing them?)
ran sfc /scannow
reran the tool, same things found / fixed
did steps I found on the web - stop services, delete things in the software download folder
still can't get windows update to work. advice short of reinstalling the OS?