Eddy,
This is more likely to inflame user before getting to any help given - even reinstalling is potentially a step to far and there is another option that could be tried first.
@ Pete Le Boydre
- Lost, Forgotten (or didn't set) Password and avast is calling for a password.
Ordinarily this would entail reinstalling avast, you may be able to remove a file C:\ProgramData\AVAST Software\Avast\aswresp.dat. Before you can delete it you would need to disable the avast self-defence module, AvastUI > Settings > Troublesooting.
If that doesn't work you would need to boot into safe mode, where avast doesn't start and remove it.