So,
I edit the question and I hope it makes more sense now. The suggestion to look at another question did not help me, because my problem is different.
My situation:
I inherited an older Sony Vaio laptop. There is installed Ubuntu on it, but do not have access to it, since I dont have the password.
I would like to reinstall Ubuntu, so I can use the laptop.
I did create a bootable USB with Rufus. I tested it on other laptops and it is bootable. But when I restart the Sony Vaio, it do not boot from USBand it leads me always to the login. SO, It is not possible for me to reinstall new Ubuntu. I have tried to press F11 F12 F9 F2 ESC and Shift. None of this works to help me reboot, except ESC give me access to GRUB.
Can someone suggest IF and What I can do to use this machine again.
Regards
