Gigabyte MB-Windows 8 OS option in BIOS..crashes?

Quick question. I have a Z77-D3H motherboard. I have been having crashes, mostly when playing BF4 and when the game starts up. When I mean crashes, I am talking about a hard shutdown and reboot. I did a memtest-no issues. PSU is relatively new. I was just playing around in BIOS tonight and saw that my OS was set to "Other OS"-I then selected Windows 8 option and I have been playing bf4 without it crashing. Literally I didn't have that option set when I first came home from work and it crashed on me 3 times in a row without even getting into the game.

I never heard of this before or else I would have looked in there...could that have been causing crashes?

System is I73770K
16 GB Ram
GTX 660 graphics card
Windows 8.1.