It's internal right? Well, you will need the drivers from the manufacturer. If that doesn't work, try added a port for the modem in Control Panel -> Ports. Use the settings that win98 uses (from Device Manager in 98) and then try detecting the modem again. Also, if it is plug and play, try disabling the PNP on the modem (if possible). You may also have to install the ISPPNP driver if it is ISA PNP and can't be changed to NON PNP mode.