:-[ Hello am new to this site, when I registered for the download lost the Key number, what do I do now?
Hi and welcome Pollyanna,
i guess if you have deleted the e,mail that had the password then you will have to re-register .
and this time hang on to the e,mail 
dont worry they are generated by a robot and come through almost immediately.
If you have the home version, just get a new key from avast’s website.
If you have the pro version contact your reseller.