Help with Adobe CS3!?

I am trying to install Adobe CS3 Photoshop, Illustrator, and Acrobat 8 Professional on my new imac. I first installed Photoshop and everything went just fine; however, when I try to install Illustrator, i cannot finish installing because it says for disc 2, I need to insert Photoshop CS4? Why is this? If anyone could help me that would be great! Thanks!