please help

i’ve had no computer for the last 6 months, but i’ve used avast home edition for the last 2 years, i’m now getting message, invalid, expiried august 2007, its telling me to enter my passcode to update, but i don’t have it anywhere, can someone please help me
many thanks
Mandy

Just register for a new key

http://www.avast.com/eng/home-registration.php