Will I be able?

So I'm going to buy CoD 1 for my laptop through Steam, it's one of the only games that I can play in my laptop and that I like.
So my question is, if I buy it through Steam will I be able to play on multiplayer?
Because I've downloaded multiple cracked versions and everytime I try to go on any server, it says "CD Key Already in Use"
So I'm wondering if I buy it through Steam if I will be able to play online.

Yes you'll be able to play Multiplayer if you buy it directly from Steam.

You could purchase it then register it with steam. That's what I do all the time.