Sadly I never found out why this happened 
I got a new computer soon after, however i ALWAYS get the Directx6 failed and from time to time it says my computer is also running at 113mhz, no matter which of the games i try to install. It may be the files on the cd are corrupted? I don't know I'm no good at that sort of thing, however if your disc is terribly scratched OR you have a feeling that the disc is the problem you are fully entitled to download the game again (Idk wherefrom, Limewire perhaps?) as you have already paid for it and you will only be running one of the programs on one computer, it's all in the terms and agreements if you can be bothered trolling through them 
If none of that works try a manual install rather than the setup wizard and change all the variables you can, I'm sure in the end it will come out ok 
