Microsoft Knowledge Base Article 311272 contains the following summary:
The DevCon utility is a command line utility that acts as
an alternative to Device Manager. Using DevCon, you can enable, disable,
restart, update, remove, and query individual devices or groups of devices.
DevCon provides information that is relevant to the developer and is not
available in Device Manager.
You can use DevCon with Windows 2000 and Windows XP. You cannot use Devcon with Microsoft Windows 95, Windows 98, or Windows Millennium Edition.