A method and apparatus for instantly-available applications in a computer system is presented. A computer that incorporates fast non-volatile primary memory for storing the application software and/or operating system, resulting in an instant-on computer is presented. Large parts of the application code and/or operating system code are stored in non-volatile write-protectable areas of the memory that cannot be modified by malicious sources, resulting in a secure computer. It solves the problem of typical computers having to load the applications from a slow device such as the hard disk to the main memory. This loading is avoided by permanently housing the applications in a non-volatile main memory. The system also solves the problem of corruption of application software areas from malicious sources. The memory system contains writeable and write-protected areas and a memory controller that controls the access to the various regions of the memory.