When you view device information on your Windows-based computer using Device Manager, you may see an unknown device listed next to a yellow question mark. Determining the cause of this unknown device can be difficult, because there are few indications of what could be creating it. This article describes the possible causes of an unknown device being listed in Device Manager.
The most common reasons Device Manager may list a device as unknown are:
The Device Does Not Have a Device Driver
When a device driver for a device is not available, Device Manager displays the device as unknown, and places it in the Other devices
folder. This is very common with Universal Serial Bus (USB) and Institute of Electrical and Electronics Engineering (IEEE) 1394 composite devices. Also, a status of "Error Code 1" or "Error Code 10" may be displayed when you view the properties of the device in Device Manager.Note
Most USB and IEEE 1394 devices are designed to function properly without additional device drivers, because they are configured and enabled by the drivers included with Windows for these bus types. However, an additional device driver is needed if the device does not fit within the defined and supplied Windows class drivers. If the bus is unable to identify the device, it interprets the device as a composite device, and reports it as such in Device Manager.
You Are Using a Windows 98 or Windows 95 Device Driver
You cannot use virtual device driver (.vxd) files common to Windows 98 or Windows 95 drivers with Windows 2000. If you attempt to install them on your Windows 2000-based computer, the device may be listed as unknown in Device Manager. This usually occurs when the device driver manufacturer does not properly differentiate between the two drivers, or assumes that Windows 2000 is capable of using Windows 98 or Windows 95 .vxd files.
Unrecognized Device ID
Every hardware device has a special identifier used by Plug and Play. This identifier can consist of a number of different types, such as vendor ID,
device ID, subsystem ID, subsystem vendor ID, or revision ID. If a device ID is not present, or your Windows 2000-based computer does not recognize the device ID, Device Manager may list the device as unknown.Note
Software programs that require virtual hooks into the hardware may create these devices. For example, Compaq Insight Manager creates virtual devices to communicate with and monitor the hardware. Upgrading a computer that has Compaq Insight Manager installed to Windows 2000 may generate an unknown device in Device Manager, because older versions of the software do not supply the proper definitions for these virtual devices.
Devices that bridge between bus types, such as a device driver that permits a parallel port device to emulate a Small Computer System Interface (SCSI) or ATAPI bus, are also known to generate an unknown device in Device Manager.
Faulty Hardware or Firmware
Possible scenarios where faulty hardware or firmware could cause unknown devices to be listed in Device Manager are:
Virtual Device Created with Software
Software only device drivers do not expose a device ID, and there is no standard method for installing these devices. Some manufacturers install the device using the InstallShield installation program, or a similar method. Note that software installed by other methods may not be completely deleted when the device is removed in Device Manager, and it may require you to check the registry on your computer and verify that all entries have been removed.
Use any of the following methods to determine if an unknown device is being created by software:
- While not 100 percent reliable, starting your computer in safe mode can be one of the easiest ways of determining if the unknown device is being created by software. When starting your computer, press F8, select Safe Mode, and then press ENTER. If the unknown device is no longer listed in Device Manager, then it is likely that the unknown device is not hardware.
- If you suspect a particular software program may be creating the unknown device, check the Startup folder on your computer to see what programs are configured to start at boot. Also, checking the menu bar can give you an indication as to what programs are automatically started, however, remember that some programs that may be configured to start at boot do not appear in the Startup folder.
- The System Information Tool can be useful in diagnosing the cause of an unknown device. To run the System Information Tool:
You should then check the event log for errors relating to any of these programs to see if there is one that is not working properly. If you find a related event, uninstall the associated program. Note that the fact that a program is creating an unknown device is not an indication that the program does not work, unless the program depends on the device to start the associated program.
- Click Start, point to Programs, point to Administrative Tools, and then click Computer Management.
- On the Computer Management dialog box, click the System Information folder, double-click the Software Environment folder, and then double-click the Startup Programs folder.
- A comprehensive list of every program configured to start at boot is displayed.
- You can view each component in your computer, including the drivers needed to make the components work. To view the components installed on your computer:
- Click Start, point to Programs, point to Administrative Tools, and then click Computer Management.
- In the Computer Management dialog box, double-click System Tools.
- Double-click System Information, and then double-click the Components folder.
- Check the Problem Devices folder, located under the Components folder.
NOTE: Follow the steps on the previous method to view the Components folder.
The following columns are listed:
- The Device column lists the common name for the device, or the name of the device driver associated with it.
- The PnP Device ID column lists device IDs such as Peripheral Component Interconnect (PCI) ID, Industry Standard Architecture (ISA) ID, an ID for some other bus type, or an unknown type.
- The Error Code column lists the error code associated with this specific problem. In many situations, the Device Manager error code helps determine what created the unknown device. For example, if your computer generates a "Bad or missing device driver" error message, three types of entries may be listed in the Problem Devices folder, depending on the device type:
- PCI PnP Device ID:
Device Name | PCI\VEN_00000&DEV_0000&SUBSYS_00000000&REV_00\0&0000 | Error code
- ISA PnP ID:
Device Name | ?\PNP0000\0
- Bad or Incompatible Device Driver:
Device Name | ROOT\UNKNOWN\0000
- Information listed in the Setupapi.log file can be helpful in identifying what may have created the unknown device, as long as the device has a meaningful name. Sometimes the device name listed can be misleading. For example, a device may be listed as a serial device in Device Manager, when in reality it is not related to a serial port. This usually occurs when a partial Plug and Play ID is available, and Device Manager interprets it as a serial device. This interpretation can occur because of a compatible ID specified by the device. Again, this can be corrected by locating the startup program that may not be behaving properly.
Note that simply removing the unknown device in Device Manager does not work if a software program is creating the unknown device. You must uninstall the program that creates it, and then restart your computer. Also, if the unknown device does is still listed after you restart your computer in safe mode, contact Microsoft Technical Support for assistance in removing the device.
Isolating hardware devices is less complex than virtual devices, and you can use either of the following methods:
- Remove hardware devices from your computer one at a time until the unknown device is no longer listed in Device Manager. Note that this method may be slow, and is not always reliable.
- Check if the device driver is digitally signed. If during the device driver installation, Windows 2000 detects that a device driver is not digitally signed, the following error message is generated:
Note that a device driver that has been digitally signed could still be listed as an unknown device in Device Manager. Also note that the user may not see this error message if it has been disabled.
Note Information about digitally signing device drivers is available at the following Microsoft Web site, and by using the Device Driver Kit (DDK) tool:
It is possible to block the installation of unsigned device drivers, which may be a good approach on mission-critical servers to prevent deliberate attempts to destabilize the server. To prevent the installation of unsigned device drivers:
- Click Start, point to Settings, and then click Control Panel.
- Double-click System, and then click the Hardware tab.
- Click Driver Signing, and then click Block - Prevent installation of unsigned files.
- Click OK, and then click OK.
To view a list of loaded devices not digitally signed, use either of the following methods:
View the Setupapi.log file for entries resembling the following entries:
The file (D:\WINNT\inf\ntapm.inf) is not digitally signed, ignoring driver date.
Installing section epatapi_inst from d:\documents and settings\user name\my documents\parallel port test drivers\epatapnt.inf
An unsigned or incorrectly signed driver (d:\documents and settings\user name\my documents\parallel port test drivers\epatapnt.inf) was installed for Parallel ATAPI Adapter.. Error 0xe000022f: The third-party INF does not contain digital signature information.
Copying file d:\documents and settings\user name\my documents\parallel port test drivers\epatapnt.mpd to D:\WINNT\System32\DRIVERS\epatapnt.mpd.
An unsigned or incorrectly signed driver (d:\documents and settings\user name\my documents\parallel port test drivers\epatapnt.mpd) was installed for Parallel ATAPI Adapter.. Error 0xe000022f: The third-party INF does not contain digital signature information.
where user name is a user name.
Use the Sigverif.exe tool, which permits you to create a log file listing all of the unsigned drivers installed on your computer. The Sigverif.txt log file created by the Sigverif.exe tool is located in the %SystemRoot% folder, and can be viewed by using a text editor (such as Notepad). To run the Sigverif.exe tool:
You may experience a delay while your computer compiles a comprehensive list of unsigned drivers. Check the list of unsigned drivers, and then check if the driver manufacturer has an updated driver that is digitally signed.
- Click Start, click Run, type sigverif, and then click OK.
- Click Advanced, and then click Look for other files that are not digitally signed under the Search tab.
- Click to select the Include subfolders check box, and then click Browse.
- Locate and then click the %SystemRoot%\System32\Drivers folder, click OK, and then click Start.
USB devices based on earlier versions of the USB specification may create ghost devices which appear when the device is connected, and then disappear when the device is disconnected. Also, the device may work just fine, but may create a disassociated unknown device, which is usually caused by either outdated or misconfigured firmware. In this case, contact the device manufacturer for updated firmware.
Ghosted devices may also appear if the user manually installs a driver for a Plug and Play device that the computer has already detected and installed. Normally, Plug and Play devices are not listed when you manually install devices using the Hardware Wizard. Because users do not see their device listed, they may assume that it is not supported, and then force an installation by using another device driver, causing the ghosted device to appear. Deleting the ghosted device generally solves this issue.
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.
기술 자료: 244601 - 마지막 검토: 2007년 5월 7일 월요일 - 수정: 4.6
- Microsoft Windows 2000 Server
- Microsoft Windows 2000 Advanced Server
- Microsoft Windows 2000 Professional Edition
- Microsoft Windows 2000 Datacenter Server
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