So about a year ago, I bought Vegas Pro 12 via downloading (no physical disc) to my desktop PC. I'd like to install it on a laptop I just got last week. Do I download the trial version at Sony's website, and activate it with the password key? What if I've misplaced that key? How do I retrieve it?
Thanks,

There's an account in Sony with your name on it. It lists your DLs with the needed information to reload to another machine including key #'s.

you just need to know the information to get into your Sony account.

I usually go to the "Updates" page and download the current version from there. Then, yes, you simply install and activate with your serial number.