what hard drives are permanently located inside the system unit and are not designed to be removed unless they need to be repaired or replaced?

The hard drives that are permanently located inside the system unit and not designed for removal are typically internal hard drives or solid-state drives (SSDs). These drives are installed directly onto the motherboard or into specialized drive bays and are used for the primary storage of the operating system, applications, and user data. Unlike external drives, internal drives are meant to remain in the system until they need maintenance or replacement due to failure.