The BIOS have nothing to do with the OS, it's other coding layer, and the OS can't "disable" the HDD since it have their own firmware on microcontroller. I would suggest: if you can boot from CD like you say, you can: - Flash the BIOS. See your board and download from oficial site; - Reboot and make a low-level dump of your HDD (you can use diskdump for this); - Set your BIOS to standard config's, but legacy boot and the SATA port that your HDD where; - Download the image of 5.6 from Calgary mirror (don't download from US mirrors); - Try install.
If you can't, so: your HDD are broken or your hardware (maybe motherboard) are broken. Greeting, Luiz.
