@gcm_rukawa11, uh? old bios in a g75vx?! then can you find the option similar to 'Disable UEFI Boot' in boot options? try to disable UEFI Boot and proceed.
edit: here's what's in the FAQ support page regarding
How do I boot to DOS with USB Flash drive or USB CD-ROM?1. Enter the BIOS setup menu by pressing and holding F2 key when powering on.
2. Switch to "Boot" and set “Launch CSM” to Enabled.
3. Switch to "Security" and set "Secure Boot Control" to Disabled.
4. Press F10 to save and exit.
5. Press and hold ESC key to lunch boot menu when the notebook restarts.