HD info lost when booting from floppy.

When I attempt to boot from a bootable floppy with CD ROM drivers, the BIOS loses HD information and recognizes the CD as C drive. I have replaced the HDD, FDD, CDD, Power Supply and MB. The BIOS sees the HD okay when NOT booting from the floppy. I have also swapped the bootable floppy. The only thing left to replace is the case. Is it possible the case is causing a short? Any ideas? Thanks!