After you upgrade from Microsoft Windows NT 4.0 to Windows XP, multiple entries for a modem may exist on the
Modems tab of the Phone and Modem Options tool in Control Panel. However, you may only have one modem, and only one of the entries may be valid and work correctly.
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This problem can occur because of an erroneous registry entry in the Windows NT 4.0 registry. Because of this entry, Windows XP Setup cannot discover if the modem was correctly installed as a Plug-and-Play modem.
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To work around this problem, remove all of the modem entries, and then restart your computer to redetect the modem.
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Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
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