Hmmm...I replaced the hard drive, and now it won't boot at all even in CD mode. Of course, the hard drive isn't formatted yet, but I thought I could at least boot off of my OS X cds and install the operating system. Maybe the jumper pins have to be set to master instead of the "cable select" option. But the instructions with the drive said for Macintosh to use cable select.
This really doesn't make sense to me now.