Here's a question that's probably been asked before a zillion times: I just got a new Mac for my work, have tons of PAID FOR plug ins that were bought by the folks prior to me and they didn't keep any of the reg codes- I have the purchase orders for them, not the codes. How do I get plug ins from computer a to computer b and have them work?
8.5 GB RAM
Final Cut Studio 6.0.4
I've done this many times and it can be quite a time-consuming pain when dealing with dozens of titles on several machines ... even more so if much time has passed since the original purchases since plugin titles often change hands among developers.
The good news - very many AE plugins show the current registration info by just clicking the "About" or "Help" buttons within the plugin interface. In some cases, you can even use that info to re-install, but at the very least, you can jot it down or screen grab it since that'll by far be the best info to provide to the developer to get current registration info and/or plugin versions.
The bad news - When the above doesn't work, POs aren't always as useful as you might expect since every developer has different procedures ... gather all the info you possibly can (i.e., names of & email addresses used by former staff during purchases) and get organized before you start emailing or calling.
Considering how often plugins are updated, sold to other developers, or any one of other scenarios that create similar predicaments; you might pick one email address, one user name, etc. (that are each unlikely to change frequently), stick to them throughout all your software purchases/registrations and keep track of all that info.
If you're thinking something along the lines of "but I'm an editor, man!", you might consider whether you're the person who should be doing all this ... or might it be the production manager, studio manager or whatever that person is called in your environment?