Hello,
I’m actually searching some help, I’m the only admin of my laptop, and avast ad create a session under avastsoftwareupdater which i could’nt erase and today when i open my laptop my session was gone and there was only avast session which require a password which i don’t have. Can you help me out ! I’m running on windows 7!
Thanks 
If possible boot into “safe” mode (pressing F8 repeatedly) then try a repair.
Control Panel>Uninstall a Program>double click “avast”>click “repair”>reboot. 
does’nt work
my session still does’nt show up. There only avast session!
What does not work? (Safe mode??) Might help to post a screenshot of your avast! session so we can see what you see.