I bought a Windows 8 pre-installed Lenovo ThinkPad that I want to downgrade to Windows 7. But when I tried to boot it from Windows 7 USB flash drive, I couldn’t get boot into it. It kept booting back to Windows 8, instead of starting the Windows 7 installation process. What was wrong?
Turned out, it’s because the secure boot is enabled to UEFI only that doesn’t allow any legacy system to boot up. If you want to downgrade your Windows 8 ready computer, you would have to disable the Secure Boot, and set the UEFI boot to allow both UEFI and Legacy systems.
On my ThinkPad in particular, I had to go into BIOS → Security, and disable Secure Boot there (Figure 1).
And go to Startup, to change the UEFI/Legacy Boot option to Both (Figure 2).
Once I’ve done that, I was able to boot into Windows 7 installation USB flash drive and start off the downgrading process.
UEFI, stands for Unified Extensible Firmware Interface, is a software middleware between an operating system and the platform firmware. It’s meant to completely replace the ancient BIOS firm interface but in practice it still provides the legacy support for BIOS services. Windows 8 is the first operating system that introduces the support to UEFI but it was caused quite a buzz when Microsoft announced it last year.