I noticed there's some settings specifically for Windows 8 within BIOS. Was it these you're referring to?
Yes, these are the kind of settings that I am referring to.
I would recommend taking the following steps:
1: Update BIOS
2: Set SATA Controller(s) to AHCI Mode (unless you are planning on using a RAID Array in which case set them to the RAID Option.
3: Set Windows 8 Options (if you are installing Windows 8 or 10)
4: Check that CPU and RAM are running at correct speeds.
5: Any other BIOS settings that you wish to change*
6: Save and exit BIOS
7: Install OS
*I would strongly advise against setting the Fast/Ultra Fast Boot option at this time. You can set it later, once the system is up and running properly. A quick note, if you find that you are struggling to get into BIOS once you have Windows installed then use the Windows Recovery Option to enter the UEFI BIOS. There are a few steps to using this procedure and if you find that you need guidance, ask and I will take some screenshots and post more details for you.
You shouldn't need to add any AHCI drivers during the install so don't get hung up on this aspect unless it comes up.
Once you have Windows installed I would also recommend that you avoid using any of the Gigabyte Apps that come on the installation DVD. They are not really necessary and can cause more problems than they solve. Once you have had the system up and running for a while and you are more comfortable with how the PC is running, then you can play around with them, if you feel the need to do so. I don't use them at all.
As I stated earlier, it is easier if you do not attach any other SATA devices during the OS Install especially if you start running into problems. These can be added once Windows is up and running.