You don’t have to pay again just to download the program, get it here http://files.avast.com/iavs5x/avast_premier_antivirus_setup.exe, but you will have to enter your license again.

Try this if you didn’t save the license.avastlic file - Resend avast License http://www.avast.com/resend-license-paid.php, you will need to enter the email that you used when purchasing the license, e.g. the one that the original email with the link was sent.