[Aimee Wilbury]

Do you have another computer to work with? If so, and if you don't have 5000 discs, you might be able to just re-burn them.

Could you swap the optical drive around and see if another one will read it? (Optical drives are pretty cheap, at least for PCs.)

I'm not familiar with Macs, or I'd help more. Did you change anything other than the OS? Maybe flashing the BIOS? (I don't even know if there is a BIOS in Macs.)