"Error 720" Error Message When You Try to Establish a Dial-Up Connection to the Internet

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Article ID: 810979 - View products that this article applies to.
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This article applies to Windows 2000. Support for Windows 2000 ends on July 13, 2010. The Windows 2000 End-of-Support Solution Center is a starting point for planning your migration strategy from Windows 2000. For more information see the Microsoft Support Lifecycle Policy.
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SYMPTOMS

When you try to use a dial-up connection to connect to your Internet Service Provider (ISP), you may receive the following error message during the "Registering your computer on the network" portion of the connection agreement:
Error 720 - the connection attempt failed because your computer and the remote computer could not agree on PPP control protocol.
Additionally, when you view the devices in Device Manager, you may notice a yellow exclamation mark (!) over the icon for the WAN Miniport IP (#2) device.

CAUSE

This issue may occur if the TCP/IP protocol has become unbound from the dial-up adapter, or if a conflict is created when a second WAN Miniport IP device driver loads.

RESOLUTION

To resolve this issue, uninstall the TCP/IP protocol, remove the second WAN Miniport IP device, and then reinstall the TCP/IP protocol. To do so, follow these steps:
  1. Uninstall the TCP/IP protocol. To do so:
    1. In Control Panel, double-click Network and Dial-up Connections, right-click Local Area Connection, and then click Properties.
    2. Under Components checked are used by this connection, click Internet Protocol (TCP/IP), and then click Uninstall.
    3. Follow the on-screen instructions to uninstall TCP/IP.
    4. Restart the computer when prompted, but click No if you are prompted to allow Windows to enable a protocol.
  2. Right-click My Computer, and then click Properties.
  3. Click the Hardware tab, and then click Device Manager.
  4. On the View menu, click Show hidden devices.
  5. Under Network adapters, there should be no WAN Miniport IP devices. If a WAN Miniport IP device is listed, continue to the following step. If no WAN Miniport IP device is listed, go directly to step 16.
  6. Click Start, click Run, type regedit in the Open box, and then click OK.

    Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
    322756 How to back up and restore the registry in Windows
  7. Locate the following registry subkey:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}
  8. On the Registry menu, click Export Registry File, type backup-key in the File name box, and then click Save.

    Note You can restore the changes that you make to this registry key. To do so, double-click the backup-key.reg file that you saved.
  9. Click each of the registry subkeys under this key, and then view the Data column of the DriverDesc value to determine which of the subkeys corresponds to WAN Miniport (IP). For example, the 0005 subkey.
  10. Right-click the subkey whose DriverDesc value data is WAN Miniport (IP) (for example, right-click 0005), and then click Delete. Click Yes to confirm that you want to delete the key.
  11. Quit Registry Editor.
  12. Right-click My Computer, and then click Properties.
  13. Click the Hardware tab, and then click Device Manager.
  14. On the View menu, click Show hidden devices.
  15. Under Network adapters, right-click WAN Miniport (IP) and then click Uninstall. Click OK to confirm that you want to remove this device.
  16. Reinstall the TCP/IP protocol. To do so:
    1. In Control Panel, double-click Network and Dial-up Connections, right-click Local Area Connection, and then click Properties.
    2. Click Install.
    3. In the Select Network Component Type dialog box, click Protocol, and then click Add.
    4. Under Network Protocol, click Internet Protocol (TCP/IP), and then click OK.
    5. When the protocol is installed, click Close.
  17. Reset the modem by turning the power off and then on, or for an internal modem, restart the computer.
  18. Test your Internet connectivity.

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Article ID: 810979 - Last Review: October 30, 2006 - Revision: 3.4
APPLIES TO
  • Microsoft Windows 2000 Professional Edition
Keywords: 
kbprb KB810979

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