How do I change my CD Key?

So, I got global banned for the first time along with several others, and I notice everyones saying, "Well, there goes another 10 dollars."
Which raises the question, where are you buy CD Keys for Arma2/OA from for $10?

I had a friend who got banned the other day, and apparently according to him, he opened his registry and generated his own Key and was unbanned in 10 minutes. However I don't know the legitimacy of his claim.

I don't care if I have to buy a key, I just would like to know where to get them from, and how I can change it without having to completely reinstalling the game through steam.

Thanks.

Yeah would be cool to know where i can get a new key for 10 bucks

Just create a new steam account and go to the "Add game" button on the bottom left, and hit Activate a product on steam. You'll already have the files on your computer and not have to reinstall.