What is the goal of Comdlg32 ?

Hello everybody,
I have developped a VB6 program which gathers some utilities for reef aquariums.
That program needs some DLL and OCX which are not available in some light Windows versions; among others : comdlg32.ocx.
Of cause I built a zipped package in order to setup the missing libraries but this seems to be too difficult for some users.

So I developped another small program to download and install the missing libraries.
This program has not any declared component in VB6 IDE.
However when run on a PC without comdlg32 installed the program claims for comdlg32 !

Is comdlg32 required even if it is not a declared component ?
Which are the VB6 functions that may need comdlg32 ?
How may I install comdlg32 from a program that requires comdlg32 ?

Thanks in advance for your help