C&C Generals:Zero Hour

Ever since I bought this game, I've had nothing but problems with it. I finally got it working properly for about a year then I had to reformat my computer and now I can't get it to work at all. The game will auto run but won't go into the game. It keeps telling me that there is no disk in the drive. I have all of the updates and I've even gone as far as getting new cd/rom drives. What the hell is going on? Why won't this game work properly? I can't even find a place that sells the game in case I want to replace it. My system is more than compatable with the game but it just won't work. Any ideas?