Avast update problem, stucked system, blocked windwows startup, freezes Computer on startup

Avast has a software design problem on version 7, if you can start windows uninstall it before update, look for prior version if you like avast: If you already updated and your system is stucked ( not starting) then start on safe mode, uninstall avast or do a system restore to previous date. Optional you can try at start: "The last good configuration mode", anyway uninstall Avast.