Win 9X Dial-Up Client & Control Panel Configurations
Checking Properties of Existing Dial-Up Setup | Configuring & Checking Network Section of Control Panel
Control Panel: Add/Remove Dial-up & Network Components | Control Panel: Modems Section & Device Manage
Control Panel: Modems Section & Device Manager
You generally want to do your modem configuration in the dial-up properties. You would go to the modem section of the control panel to reinstall a modem and/or remove "ghost" modems that aren't actually installed even though the computer thinks that they are installed.