Half-life key

[Hyper Chi Aura]

ok...i got steam...and i got esf....i click on esf...bring me to steam and i click "i already own this game" or sometin like that....I type in my cd-key EXACLTY like im supposed to...and when i do it says "this cd-key" is invalid....so i try it again, now it says there a duplicate,...neoe kno how to fix this problem?

 

[Super Bolt V2]

It's either used before or your mistaking 0's (number) for the letter O , if not you'll have to contact steam