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Article ID: 150808 - Last Review: September 30, 2013 - Revision: 1.1

This article was previously published under Q150808
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Windows NT 4.0 Remote Access Service (RAS) includes support for Unimodem modems. If you attempt to use a device with RAS that is not supported by Unimodem, you may need to configure RAS to use the Modem.inf file instead of using Unimodem.


To use the Modem.inf file instead of Unimodem in RAS, perform the following steps:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.
  1. Start Registry Editor (Regedt32.exe) and go to the following subkey:

  2. On the Edit menu, click Add Value.
  3. Type the following values:

    Value Name: EnableUnimodem
    Data Type: REG_DWORD
    Value: 0
  4. Quit Registry Editor and restart Windows NT.

    NOTE: Once EnableUnimodem=0 is set in the registry, you have only the option to select from the list of modems (Modem.inf) in RAS properties. You do not have the Have Disk or Install Modem option. This behavior is by design.

    If your modem does not appear in the list of modems, download the modem manufacturer's latest .inf file to Modem.inf and place it in the Winnt\System32\Ras folder, or add the settings to the existing Modem.inf included with Windows NT. In either case, be sure to back up the original Modem.inf file before making changes.
  5. Run the Network applet in Control Panel and choose the Services tab.
  6. Select Remote Access Service from the list of installed services and click the Properties button.
  7. Remove any ports currently defined in the RAS Setup dialog box.
  8. Click the Add button and re-add the ports. RAS will now use the Modem.inf file to retrieve initialization information for the devices you add.

  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 4.0 Standard Edition
kbnosurvey kbarchive kbnetwork KB150808
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