older game purchases

[EXTERMINATUS]

I bought some games before steam existed, these games were later added to steam, i don't want to buy these games AGAIN, is there a way to transfer/activate these games on steam without having to purchase them AGAIN? games include: tron 2.0, overlord 1, overlord 2, tron evolution,

[FFL2and3rocks]

Click "Add a game" in the bottom left of the Steam window, then "Activate a product on Steam" and enter the CD key that came with the game.

If it doesn't accept the key, or you don't have one, you're out of luck.

[EXTERMINATUS]

Thanks, i tried the add option but tells me the product code is invalid, and overlord 1 and overlord 2 never came out with cd keys

[Cathulhu]

Retail / Digital CD Keys What is a CD key and where can I find it? Which retail / digital CD Keys are accepted on Steam? (Link)
If it's not on the list there, it cannot be activated on Steam

[EXTERMINATUS]

Ok thanx