Whether I use Legacy or UEFI Mode, I can't get my PC to boot from flash drive, which was NEVER a problem before. It worked just fine, but now I tried Win Toolkit, RUFUS, and WinUSB maker with 2 different Windows 8.1 Update 1 ISO files (one by me and on by murphy). Neither worked. I reset BIOS settings completely, but that also didn't work - my PC sees the flash drive, but it just won't boot from it, without any error. If I force that flash drive to be the only boot drive, then it just takes me back into UEFI/BIOS without any error messages... Any ideas?