Windows7 hangs on Startup

[JohnASmith]

My Windows7 hangs on Startup.  The Event Viewer shows that an Avast Service failed to load.  If I restart and run Repair the system will start until next time when it does the same thing.  Any suggestions?   

[Lisandro]

I suggest an installation from the scratch:

1. Download the latest version of avast! Uninstall Utility and save it.
2. Download the latest avast! version and save it.
3. Uninstall avast from Control Panel (if possible). If, for any reason, you can't run it, try booting in Safe Mode and doing it from there. Anyway, boot after that.
4. Run the avast! Uninstall Utility saved on 1. If, for any reason, you can't run it, try booting in Safe Mode and doing it from there. Anyway, boot after you've run it.
5. Install avast! using the setup saved on 2. Boot.
6. Register your free copy or add the license key for Pro.
7. Check and post the results.

Which was your old antivirus before avast?
Any other security program?
Which is your firewall?

[JohnASmith]

Thank you for the detailed response.  First, this was a fresh install of Windows 7 and the only antivirus that has been installed is Avast although a previous version.  I also use Adaware but it seems to coexist with Avast quite well on other PC's I have.  Then your questioning made me wonder if Windows Defender may be the culprit.  I did uninstall and reinstall exactly as you suggested and also disabled Defender.  It might be a couple of days before I will know for sure one way or the other but I will report back.  Thanks again.

[JohnASmith]

Unfortunately that effort failed however the Event Log no longer shows Avast as the fault so off to other possibilities.  Thanks for the great advice.