As wombat sugested...change the harddrive jumpers to master and slave.

It is fine for them to be on the same ribbon but would actually perform better if the harddrives were on seperate EIDE controllers.

The best scenario for your computer would be to set up the drives as

EIDE 0 (primary) "C" drive harddrive as master and a DVD player as slave on the same cable (perferably 80 conducter cable)

Eide 1 (secondary) 'D" harddrive as master and the other DVD as slave on the same cable. (again preferably 80 conductor cable)