1. A secure instant-on computer system comprising: a processor coupled to a virtual memory system with a write-protection mechanism; wherein the virtual memory system comprises a physical memory region and a virtual memory region, wherein the physical memory region has a non-volatile main memory with write-protected region, wherein the write-protected mechanism prevents additional writes to the write-protected region after initial manufacture and/or installation, an Operating System (OS) code is stored into the write-protected region of the non-volatile main memory region before user power-up, wherein the OS code in the write-protected non-volatile main memory region is write-protected by hard-coding at least one of plurality of bits in a page-table mapping entries; wherein a mapping entry is selected from a group of reference bits, replacement information bits, and read-write-execute (RWE) bits, wherein the read-write-execute bits indicate a permissions to read, write and execute the user application code in a selected page; an application configuration and a session data for each of the OS code in non-volatile write protected main memory, and a secure read-write access to the writ; and, protected region, the configuration data specifies selected options that control the execution of each of the OS code and the session data specifies information about previous completed or suspended executions of each of the OS code; wherein the secure read-write access to the write protected region selectively permits the processor to write to the write-protected non-volatile main memory region which contains the application configuration and the session data; wherein the OS code is made secure by preventing writes to the non-volatile write protected region in which the user application code is residing; a malicious code cannot be transferred to the non-volatile write protected main memory region which contains the OS code by the write-protection mechanism and the user application code is directly executed from the non-volatile write-protected region at power-up thereby resulting in an instantly-available the OS code.