How to move avast licence to new PC

I have a a licence for Internet Security -3 PCs, 2 Years that is valid to mid 2015. I have lost the licence key and now i have one new PC without Avast security. HOW do I transfer the licence to the new PC and another e-mail address?

Retrieve the key and use it: http://www.avast.com/resend-license-paid.php

Thank you! BUT, I have to request the licence key from the original e-mail address and the licence key is only valid for that email-address so I cant get it for me.
Avast seems not to understand that people change PCs and addresses! What can I do?

You didn’t keep a copy of the license file on each machine?

If you changed email address is it possible to use mail forwarding/collection?

Do you have the receipt or original order?

copy license.avastlic to the third system and use it.

Login and change your email: https://my.avast.com:443/#faq