I can't guess the before or after settings but it's pretty well know if the SATA controller when changed from AHCI to IDE Emulation or back or to other will cause a boot loop.
Get back in to the BIOS and try "Defaults." If that doesn't work, look at drive controller options and set them to when it worked.
Hello. After updating Bios for motherboard (H77-D3H) to version F15 windows 8.1 does not load, it's just on a constant loop of restarting. Any help or tips how to fix it or re-installing windows is the onlt thing to do ?