OS X :: Applecare - Register It In Order To Activate It ?

When you purchase Applecare, do you have to register it in order to activate it? I bought it for my old PowerMac but never registered or even used it. So a few years later my mac took a dump and the Applecare time has expired. Or has it? Since I paid for it but didn't register it, did it start when I bought it?

I don't want to sound like someone that's trying to get over on Apple, but in the entire time I owned the PowerMac & the Applecare, I never got anything from them in the mail showing that it was active, even though I bought and paid for it when I bought the computer.