You also should remember that DOS-based programs maintain their own driver set, which works independently of Windows. Just because Windows is set up correctly doesn't mean that the program in question is configured correctly. Check the COM port settings within your program to make sure that they match what Windows was set up to use. If the Modem Diagnostics program seems to work, but you still can't dial out, there are several things that you can check. The most common cause of this problem is an incorrectly configured modem.
Modems have two phone jacks on their backs.
One of these jacks connects the modem to the wall. The other jack is designed to allow you to plug a telephone into the modem for voice calls. If the phone cord that plugs into the phone jack in the wall is plugged into the wrong port on the modem, you won't be able to make or receive calls with the modem. Another reason you might not be able to dial out is that the modem may be plugged into the wrong type of phone line. Many businesses use digital phone lines.