Unsecure system software and secure system software on the same computer system is switched between. A computer system includes one or more processors, which may not have any built-in security features, memory, and firmware. The memory stores secure system software and unsecure system software. In response to receiving a user signal, the firmware switches from the unsecure system software running on the processors to the secure system software running on the processors (and back again). While the unsecure system software is running, the secure system software is protected from tampering by the unsecure system software.