UEFI stands for Unified Extensible Firmware Interface, it is a standard firmware interface for PCs. UEFI is, designed to replace BIOS (basic input/output system). It’s designed to improve Windows boot time and overcome the limitations of BIOS. Most OEMs shipping Windows 8 / Windows 8.1 machines preinstalled with UEFI with Windows product key embedded inside. When you install Windows 8.1 from DVD/USB, your installation will detect product key from UEFI firmware (BIOS) and activate Windows 8.1 automatically. So if your PC comes with UEFI firmware and you don’t have the key, then you have to create UEFI USB flash drive installer to do a clean install.
Following are the instructions to make a bootable UEFI USB flash drive for Windows 8 and Windows 8.1
Step 1. Download and save the Rufus program. (download here)
Step 2. Connect your USB flash drive.
Step 3. Click on the browse icon and select your Windows 8.1 / Windows 8 ISO image file.
Step 4. Under Partition scheme and target system type, select GPT partition scheme for UEFI Computer
Step 5. Under File system, select FAT32
Step 6. Leave the rest of options as default.
Step 7. Click on Start button.
Step 8. Now sit back, relax and wait for the process to complete. Once the process is finished you can eject your pen drive and install windows.