Final answer:
The next step after completing POST for each adapter card with BIOS in Windows XP is loading the bootloader and transferring control to the operating system's kernel, resulting in the operating system starting up and running.
Step-by-step explanation:
After completing the POST for each adapter card that has BIOS, the next step in the sequence for a Windows XP computer is to load the bootloader. The bootloader is responsible for loading the operating system from the storage device, such as the hard drive or SSD.
Once the bootloader has loaded, it then transfers control to the operating system's kernel. The kernel is the core component of the operating system that manages the system's resources, such as memory, processes, and hardware devices.
From there, the operating system boots up and starts running, allowing the user to interact with the computer and use various applications and programs.