Run malwarebytes for the virus you're having!
As for Avast, if U want to uninstall, try by cmd:
Start>Run .
Type cmd and ok
Type:
wmic
Type:
product get name
and wait for a list of installed apps.
Type
product where name="name_as_listed_above_of_your_avast" uninstall
or
product where name="name_as_listed_above_of_your_avast" call uninstall
Type in Y and enter. And then type exit.