Hi MrDerfla, I am Rob, a volunteer and a 10 time and dual award MVP specializing in Windows troubleshooting and Bluescreen analysis. Please remember as volunteers we are not responsible for the development of Windows or the computer hardware and drivers. If you will work with me then I will be here to help until the issue is resolved.
I would uninstall Avast and then run its maker's removal tool. Use Windows Defender which in Windows 8/8.1 & 10 is a full antivirus.
Contact Avast Support and their forums.
Avast - Uninstall Utility
http://www.avast.com/uninstall-utility
List of anti-malware program cleanup/uninstall tools
http://answers.microsoft.com/en-us/protect/wiki...
Uninstallers (removal tools) for common antivirus software
http://kb.eset.com/esetkb/index?page=content&am...
Then do these:
Windows Key + X - Command Prompt (Admin) OR Windows PowerShell (Admin)
(Run these one line at a time.)
SFC /scannow
Note if that shows uncorrected errors - continue regardless.
When that completes run these :
DISM /Online /Cleanup-Image /CheckHealth
DISM /online /cleanup-image /scanhealth
DISM /online /cleanup-image /restorehealth
Note if that shows any uncorrected errors - continue regardless.
Then restart the computer.
Fix Windows Update errors by using the DISM or System Update Readiness tool
https://support.microsoft.com/en-us/help/947821...
How to Repair Windows 10 Image using DISM
http://www.tenforums.com/tutorials/7808-dism-re...
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If needed :
A Repair Installation which allows you to keep the programs and data though redundant backups are always a good idea.
How to: perform a repair upgrade using the Windows 10 ISO file
http://answers.microsoft.com/en-us/insider/wiki...
Please let me know if that helps.