Bad Serial Key Given in Setup?!

So, I purchased ARMA 2 combined ops on Steam, because it was 50% off. But, when it finally finished downloading, I tried to play it. It would start up, and then CRASH to the desktop with an error message that said Bad Serial Key Given in Set-up. It is doing that for ARMA 2, OA, and BAF just wont start on its own, but I think that's because its an add on. I am re-downloading/installing now, but I don't think that will help! What do I do?!

First, try to run the combined version in steam.

I did that as well, Still didn't work.

That error comes up when the games tries to run for the first time without admin privileges and can't write to the registry. Close Steam, right click on the steam.exe (in the main Steam folder), 'Run as administrator'. When it loads up, then launch the game and you should be good to go from then on.

(edit: You can also do this with the shortcut from Properties->Compatibility, but that will give it admin rights every time it launches from that lnk.)

Ok, And can I just play BAF or do you have to have OA, because BAF is done installing downloading thingy but OA and ARMA 2 are still because I just figured why not.