Red Alert 3 invalid serial error

I recently purchased Red Alert 3 through Steam and like many of the others that have had problems with Red Alert 3, I am currently running WIndows 8 on my Alienware gaming laptop. I can get the game to run by using the compatability options but when I try to log into the online portion I get an error message stating that I have an invalid serial. I have verified the serial and changed it several times. I have even tried using my original CD key from when I purchased it years ago. However, I am still being given an error message.