In an approach to allowing a computer to boot from a user trusted device (UTD), the computer comprises a data storage device storing operating system (OS) services, and a version of an OS loader. The UTD is connectable to the computer and stores a boot loader, detectable by a firmware executing at the computer, and an OS loader, and wherein the UTD prevents an unauthenticated user to modify the boot loader and the OS loader stored thereon. The computer then, upon connection, lets the boot loader be detected by the firmware for execution of the boot loader at least partly at the computer, to cause to transfer the OS loader from the UTD to the computer, and executes the transferred OS loader at least partly from the computer, to execute at least one crypto driver for the OS, to start the OS services and complete booting of the computer.