Just something to check
not sure it it'll work, but I bet you'll try anything
open up the computer. Now you say it does it copying from hard drive to cd copier, so it seems the case it is something to do with these components.
Make sure the hard drive is on teh IDE1 channel, and the cd rom and cd copier are on IDE2 together, with the main cd drive as master, and the same with the hard drive. So all using different ribbons.
I say this, because this itself could be causing interference if you've put them on the same channel for example since of course the hard drive would work faster than the cd copier, and it could be getting confused, and splatting on the floor
So just check these and get back with how it goes