On most motherboards there are 3 IDE controllers:
Primary
Secondary
Floppy
Each controller can usually hold 2 drives, giving you a max of 6 drives. However, can you have more than 6 controllers?
What if I wanted to add a 3rd CDROM to my computer, but the Secondary controller already has 2, and the primary controller has 2 hard drives? The floppy controller obviously cant take a CDROM drive....
Meanwhile, on a totally unrelated topic, my Age of Empires CD is being gay...