Configure BIOS/UEFI
Turn on the computer
Turn on or restart your computer and watch for a message during the POST about a particular key, usually Del or a function key like F10 (e.g. HP Z4 PC) that you'll need to press to access the BIOS/UEFI setup utility. It's possible, you won't see such message at all, but a vendor splash screen instead.
Enter the BIOS/UEFI Setup Utility
After pressing the correct keyboard command, you'll enter the BIOS/UEFI Setup Utility.
Wipe the harddisk (if possible)
Some systems make wiping the harddisk possible from BIOS/UEFI (e.g. "HP Z2 PC").
Select tab "Security -> Hard Drive Utilities".
Select "Secure Erase".
Confirm your drive.
Read and comprehend the message. Choose "Secure Erase (Format NVM) Clear" in this case.
Confirm.
Confirm again.
The wipe completes successfully. Press Esc.
Select the boot mode
In this tutorial, we do not use BIOS, but UEFI-mode. For e.g. a "HP Z2 PC", select "Advanced -> Secure Boot Configuration".
Make sure "Legacy Support Disable, Secure Boot Disable" is selected.
Save/confirm your changes and exit
Exit the utility using Esc and save changes - if any.
Shutdown
If you could wipe the harddisk, the sytem tries to PXE boot (and it will fail, that's expected). If you could not wipe the harddisk, it may or may not boot (depending on whether an OS is present or not). Nevermind. We will eventually erase possible partitions in the next steps. Shutdown the PC by pressing the "power button" long enough.
