can't get os to install

[buckeye]

i recently replaced my motherboard, processor, hard drive, and cd-rom drive. i'm trying to install my os, the floppy disk is in, but when i put the cd in, it says not ready reading drive d. (d is the drive the computer read as the cd drive). what do i do to get it to read the disc?

[Raptor]

Is the CD-ROM drive properly connected? Perhaps you turned   the IDE cables around.

[merlin_2]

go in to the bios del key on boot and change the boot sequence to cdrom..