Disable unused modems
If you have multiple line license, and you have multiple modems installed, you can disable some modems if you do not want to use all of the lines. There is no need to physically uninstall the modem from your computer.
Click Windows Start button, then select Control Panel. From the Control Pannel, select Phone and Modem Options. From the dialog window, select the modem you want to disable, click the Properties button. From the Device Usage list, select “do not use this device (disable)”.