This research is to design system software modules for main memory-disk integrated system. To utilize many useful features of recent non-volatile memory, a horizontal memory hierarchy should be considered as a new approach. Main objective of this study is to design an optimized bootstrap method for the integrated memory-disk system, along with compatibility with conventional bootloader and operating system. In this memory-disk integrated system, stored files and data are accessed in place reducing duplication between the main memory and storage. Thus, previous booting sequence of loading bootstrap and operating system from secondary storage to main memory should be changed to reflect the architectural change. Our proposed technique provides compatibility with conventional system software and fast booting time by utilizing prominent advantages of the integrated memory-disk system and optimizing booting sequence for this system. To implement this method, we modified BIOS (basic input/output system) to change booting from integrated memory-disk system. We used QEMU machine emulator to simulate the proposed booting method. Our experimental results show that the proposed bootstrap method can reduce the number of instructions to execute by around ten millions, resulting in fast boot performance and keeping the core of the bootloader.