Hi,
Verify that the phone cable attached to the modem is plugged in, attached correctly, and in good condition.
Make sure that the phone jack is working. To test this, plug in a working phone and see if there is a dial tone.
Make sure you have the telephone line coming from the wall socket plugged into the line in jack on your modem, with the line out on your modem going to your telephone. If you've reversed these cables, the modem won't work. If you're unsure how to connect the lines to your modem, check the information that came with your modem.
If you are using an internal modem, verify that it is firmly seated in an expansion slot. If it isn't fully pushed in, the computer cannot recognize it.
If you are using an external modem, check the power cord and power switch, then check the serial cable and connection.
Check Device Manager to see if the modem is installed correctly.
1. Open Device Manager by clicking the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking Device Manager. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
2. If Modems does not appear in the list of categories in Device Manager, Windows does not recognize your modem. You will need to find a compatible driver for your modem and install it.
3. Check if a driver for your modem is available through Windows Update.
4. If Windows Update did not automatically detect your modem and install a driver, you will have to go to manufacturer’s website download the latest drivers and install it.
If not, I would suggest you to uninstall and reinstall the drivers for modem and check.
Refer this links for more information on how to change modem settings and how to install or remove a modem.
http://windows.microsoft.com/en-US/windows7/Change-modem-settings
http://windows.microsoft.com/en-us/windows7/Install-or-remove-a-modem
Please respond back with the status on the issue and let us know if you have any issues.
Azam - Microsoft support.