Try scanning your PC with ESET Online Scanner
then
Download Tweaking.Com - Windows Repair Portable to your Desktop and extract the folder from the zip archive.
Open the folder and run Repair_Windows.exe. Select the Repairs tab and then click on the 'Open Repairs' button.
Select the following Repairs:
- 03 - Reset Service Permissions
- 04 - Register System Files
- 05 - Repair WMI
- 10 - Remove Policies Set by Infections
- 17 - Repair Windows Update
- 26 - Restore Important Windows Services
- 27 - Set Windows Services to Default Startup
Press the 'Start Repairs' button. When all repairs have completed, you'll receive a prompt to reboot.
Reboot the PC and see if Windows Update will work.