Disabling Secure Boot
You may want to disable Secure Boot in order to install new hardware or boot from a CD or DVD. Follow these steps to disable Secure Boot:
1) Turn off the computer.
2) Turn on the computer and immediately press the F10 key repeatedly, about once every second, until the Computer Setup Utility opens.
3) Use the left and right arrow keys to select the Security menu, then use the up and down arrow keys to select Secure Boot Configuration , and then press Enter .
4) The Secure Boot Configuration warning displays. Press F10 to continue.
5) Use the up and down arrow keys to select Secure Boot , then use the left and right arrow keys to change the setting to Disable .
6) Use the up and down arrow keys to select Legacy Support , then use the left and right arrow keys to change the setting to Enable .
7) Press F10 to accept the changes.
8) Press F10 again, then press Enter twice to restart the computer.
9) As soon as the computer starts, a message appears indicating that the boot mode has changed.
10) Type the four-digit code shown in the message, then press Enter to confirm the change.