After you upgrade to Windows XP, Unimodem modems may still appear in Device Manager and be listed as "Unknown modem." You may be able to use the modem to connect to the Internet, but the connection icon does not appear and you cannot disconnect the connection.

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This behavior can occur if you are using a non-Plug and Play modem in Windows XP. Non-Plug and Play modems are not supported in Windows XP.

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To work around this issue, use either of the following methods:

•	Contact the manufacturer of the modem for an updated driver (.inf file) that is compatible with Windows XP.
•	Manually install the modem as a Standard Modem device. For information about how to do this, click Start, click Help and Support, type installing a modem, press ENTER, and then click the "Install an unsupported modem" topic.

If you are using a new (or "clean") installation of Windows XP, or you upgraded from Microsoft Windows NT or Microsoft Windows 2000, you must install the modem manually because Windows installs modems only based on a Plug and Play enumeration event.

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This behavior is by design.

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Support for older (or "legacy"), non-Plug and Play modems (identifiable by a Plug and Play ID that starts with "UNIMODEM") has been removed from Windows XP. By design, all legacy network devices are not supported in Windows XP. However, an exception was made for users who upgrade a computer with an older, unsupported modem attached from Microsoft Windows 98, Microsoft Windows 98 Second Edition, or Microsoft Windows Millennium Edition (Me). In this case, the modem is installed as an unknown modem so that basic data modem functionality is provided.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

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