So I installed a slave drive, (and then replaced a defective data cable), and went to install, and nearly through the first disk it stopped with some read error (Redundancy error, I think? If it's important, I'll check). Cleaned the disk and tried again, and same thing happened. Installed another dvd drive (since it's given me trouble in the past), cleaned the disk again and tried again. Same exact thing.

I think it's the disk. There's nothing hideous on it, but it's got the typical wear and tear of being much-loved.
Has anyone got any suggestions? If the game's gone with no decent recourse, I wont be happy.