Activation Key?

Hello. I purchased Think Tanks several years ago and I installed it on an old computer I have so my kid could play. Unfortunately, when I try to enter the activation key I have, it says it's "Invalid".

I'm sure you have a copy of my purchase records. At the time, I think I had a Comcast email account (my name @ comcast.net) Can I get a functional activation key, or is the game totally obsolete now?