Can not install other systems after pre-installing Win8 How to solve

Today, start a T430S, pre-installed WIN8 X64 system. Because some software is not compatible with the system, I have to use WIN7 instead. The strange thing is that when I use the WINDOWS PE boot disk, I can't enter it anyway when I try to enter the PE tool; the same is true for the USB version of WINDOWS PE. I have never encountered such a problem before, and the preliminary estimate of Xiaobian should be caused by security settings.
After booting into the BIOS, modify the following options, the problem is solved, the steps are as follows:
1, restart the machine, enter the BIOS
2, enter the security— > secure boot option, set its value to Disabled.
3, enter the Startup & mdash; UEFI /Legacy Boot option, change the value of the UEFI /Legacy Boot option to Both; then select the value of UEFI /Legacy Boot Priority as UEFI First.
Press F10 to save and restart the computer, plug in the U disk version PE, OK. Finally, I can enter!~
This is because the BIOS of the WIN8 notebook is different from the previous one.