This is usually not a standard COM port. It is often a or an internal modem/vendor-specific device that XP cannot identify automatically.
Good luck!
If you are installing Windows XP 32-bit on older hardware (especially industrial PCs, legacy desktops, or motherboards from the late 2000s), you might see an unknown device labeled in Device Manager with a yellow exclamation mark. pci serial port driver windows xp 32 bit