Cause - BIOS settings default to modem disabled
When optimized defaults have been loaded in the BIOS, the default setting is for the modem to be disabled. Even if the modem is installed properly, the system will not see it.
1. To enable modem functionality, enter the BIOS and navigate to Integrated Peripherals, then Onboard Device.
2. Key down to AC97 Audio and Modem and choose the setting All Enabled.
3. Press F10 to save these settings and exit the BIOS. The modem will be detected in Windows and drivers can now be installed.