I know how to make a DVD into CDs, but I don't know how to make the resulting CDs usable as install discs. Anyway, what you do is make a disk image of the DVD, then use a little tool called DMGscissor (unfortunately, no longer available for download) to split the disk image file into CD-sized disk image part files. I'm not sure how helpful my suggestion will be, due to the fact that I can't find DMGscissor anywhere.