Old Call of Duty games

[night_day]

Well, I finally updated my computer and am now very excited to try some of the Call of Duty games starting with 4. If i buy a used one, can I still play online?

[xwar]

Gets them off steam.

[night_day]

I'm cheap and don't want to drop $40 for a game that's a few years old :D

[skewed]

Just wait for Modern Warfare 2 then.