Go to BIOS.
Get computer serial number (example 1234567-595B).
Go to https://bios-pw.org/
Put your serial number and click "Get password".
You will get something like this: "Dell from serial number: UbRv8meGbVzr502t"
Go to BIOS.
Enter admin password (UbRv8meGbVzr502t).
Hit "Ctrl + Enter" (important!). Just "Enter" won't work.
Type new password and save.