To determine whether your PC is using BIOS or EFI/UEFI please follow the steps below:
1. Start your PC
2. Go to Start ► Computer
3. Navigate to C:\Windows\Panther\setupact.log
4. Open setupact.log
5. Search for this string:
Callback_BootEnvironmentDetect: Detected boot environment:
The entry found in the Setupact.log should show the boot environment: BIOS or UEFI:
Code:Callback_BootEnvironmentDetect: Detected boot environment: BIOS
Code:Callback_BootEnvironmentDetect: Detected boot environment: UEFI
Another method to determine if the machine is using BIOS or UEFI that will work on Windows 8 or Windows 2012 operating systems is to use the MSINFO32.exe utility contained in that operating system.
1. Go to Start and either use the RUN line or open a Command Prompt.
2. Type in MSINFO32.exe and click Enter.
3. The System Information Report will open on the screen.
4. Check BIOS Mode and it should show either UEFI or Legacy.