I have now talked a bit with Gigabyte support, and they gave me the standard answer of "reset CMOS, load optimized defaults (even though I said I could not reach anywhere past splashscreen on the defective bios) and try the BIOS switch on the back of the board" when I quite clearly explained what the issue was, and specifically asked how to reflash an inactive bios. I have now sent another message, suggesting the boot-good-bios-and-switch+flash-while-in-windows method, so we'll see what they have to say about that. BTW, does any of you know of a way to check which BIOS is currently active? As in backup or main.