Okay, so three yearss ago I bought C&C3, stopped playing it sometime and recently I started playing the game again but when I wanted to start playing online I couldn't freaking log on with my ID's and everything without it saying that it cant be found. So I read up online and decided to un-stall the game and then re-install it so I could fix everything. But as I got to the part where it wanted me register the game I put in my CD key and it won't let me get past it because it's "already registered." The game won't even let me re-install it with the CD key that it came with!!
What do? How do I get past this?