Re-downloading arma 2?

[Creation (DayZ) 0]

So I installed Arma 2 free from the website but It wouldn't work with steam operation arrow hear.

I put that arma 2 folder in the steam folder and now its reinstalling over it.

Its just making the file size smaller than bigger. Is there any way I can make it so that it just uses what I already have downloaded or will it have to do what its already doing?

(I'm retarded at describing situatuions, I know :$)

Thanks

[SmashT 10907]

I don't know, I had steam automatically decide to "update" the game once (re-download the entire game), even though it was already installed and fully up to date by steam the first time, I turned automatic updates off after that.