I'm thinking that bootable add in cards as your first boot is the problem. Two ways most boots are set up.
1. Drive where operating system is located first boot, (in most cases C on disc 0, zero).
2. DVD/CD drive first boot and drive with operating system as 2nd boot.
Your computer is trying to boot from your external drives.
I have never used a Gigabyte motherboard so I really don't know it's bios setup procedure or terminology.