Can't update 8.1

I switched on a computer that hasn't been used since July. There are 42 updates pending but when I try to download and install, it just goes into a loop and doesn't update. Any ideas? I tried just one update, but same result.

Turn automatic updates off. Reboot. Go into disk cleanup, select "cleanup system files", let it scan, select the box to delete "Windows Update files", reboot again. Do a manual check for updates, just select one update, see if it installs.

Have you tried the built in Windows Update troubleshooter?
Control Panel>Troubleshooting>System & Security>Fix Problem With Windows Update. Then follow the prompts