During the "POST" (Power-On Self-Test) process, the computer's basic hardware components are checked to ensure that they are functioning properly before the operating system is loaded. This process takes place immediately after you turn on the computer. However, it's important to note that the "POST" itself doesn't directly check the hard drive capacity.

The "POST" primarily focuses on checking essential hardware components such as the CPU (Central Processing Unit), RAM (Random Access Memory), motherboard, graphics card, keyboard, and other critical components. It ensures that these components are operational and that the computer can proceed to the next stage of the boot process, which involves loading the operating system.

The hard drive capacity check typically occurs later in the boot process when the BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) is accessed. The BIOS/UEFI is responsible for initializing and configuring hardware components, and it often includes a component that identifies the attached storage devices, including hard drives, solid-state drives, and other storage media.

During the BIOS/UEFI initialization, the system may display a summary screen or provide access to a setup utility where you can view information about the connected storage devices, including their capacity, model, and other relevant details. This information is displayed as part of the system information and configuration options provided by the BIOS/UEFI.

The exact location and timing of the hard drive capacity check within the boot process can vary based on the specific motherboard, BIOS/UEFI version, and system configuration. Typically, it occurs after the POST but before the operating system is loaded.