The modem may need to be reset.

1. If you have an external modem, turn its power switch off.

2. Wait a few seconds and turn the power switch on again.

3. Try to dial-up again.

4. If you have an internal modem, shut down Windows.

5. Power down the computer.

6. Wait a few seconds and turn the power switch on again.

7. When Windows finishes rebooting, try to dial-up again.