ASUS e203MAH

Entering Bootloader of ASUS E203 MAH laptop:

1. Power on the Asus S200e laptop
2. Press and hold F2 key when powering on the Asus S200e laptop to enter the bios.
3. Switch to the “Boot” tab and set “Launch CSM” to Enabled.
4. Switch to the “Security” tab and set “Secure Boot Control” to Disabled.
5. Press F10 to save and exit.
6. Press and hold ESC key to launch the boot menu while the Asus S200e laptop is powering up.

source: https://www.rgb.ie/2015/03/26/how-to-boot-from-usb-drive-on-a-asus-s200e-laptop/