DavidR
2
Just remove/uninstall on the old drive/system and install on the new drive/system and use the same license (you would have to have saved it). So long as you don’t exceed the number of PCs that your license is for it isn’t a problem as it is only active on that one system.
If you didn’t save the avast licence - 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.