i have Avast on my computer and i bought it kinda used so i dont know what email it was registered to, but it has expired anyway on how to fix this?
Well if it’s home version, just re-register it. It’s free, you can do that from the avast.com home page. key will be e-mailed to you. If it’s pro you want then you can register it there to, for a fee. It’s actually the key that is registered, so it doesn’t matter who origanally downloaded the program.
HTH
If you qualify for personal, Home, non-commercial use then just register it in your name. Complete the avast! 4 Home Registration form and you will receive an email from register @ avast.com (without the spaces) with your registration key.
If you have any anti-spam filters, etc. ensure that you add the email address or domain to the allowed/friends/whitelist etc. so it doesn’t get blocked.
If the registration has expired the program and VPS may be well out of date is out, current version is avast home 4.7.982 and VPS version 0648-2.
Actually it’s 4.7.892 
must get these fingers fixed, a little ytpo ;D