This step-by-step article describes how to troubleshoot unknown devices in Device Manager. You can use Device Manager to view the status of your computer hardware on your Windows-based computer. Unknown devices may be listed next to a yellow question mark. This indicates that the hardware is not functioning properly because the system does not know what driver to install for the hardware. It may be difficult for you to determine the cause of this unknown device because there are few indications of what might be creating it. The following causes are the most common causes of an unknown device:
back to the top Device Does Not Have a Device Driver
- The device does not have the correct device driver installed.
- The device is using device drivers from a different version of Microsoft Windows.
- The Device ID is not recognized.
- The hardware or firmware is damaged.
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 turned on by the drivers that are included with Windows for these bus types. However, an additional device driver is required if the device does not fit in the defined and supplied Windows class drivers. If the bus cannot identify the device, it interprets the device as a composite device, and reports it as such in Device Manager.back to the top Using a Microsoft Windows 98 or Microsoft Windows 95 Device Driver
You cannot use virtual device driver (.vxd) files common to Windows 98 or Windows 95 drivers with Windows Server 2003. If you try to install them on your Windows Server 2003-based computer, the device may be listed as unknown in Device Manager. This typically occurs when the device driver manufacturer does not properly differentiate between the two drivers, or assumes that Windows Server 2003 can use Windows 98 or Windows 95 .vxd files.back to the top Unrecognized Device ID
Every hardware device has a special identifier that is used by Plug and Play. This identifier can be made up 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 Server 2003-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 Server 2003 may generate an unknown device in Device Manager. This occurs because older versions of the software do not supply the correct 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.back to the top Faulty Hardware or Firmware
Scenarios of how damaged hardware or firmware might cause unknown devices to be listed in Device Manager are:back to the top 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 by using the InstallShield installation program, or a similar method. Note that software that is installed by other methods may not be completely deleted when the device is removed in Device Manager. You may have 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:
- You can start your computer in Safe Mode to try to determine if the unknown device is being created by software. When you start your computer, press F8, select Safe Mode, and then press ENTER. If the unknown device is no longer listed in Device Manager, the unknown device is probably not hardware. Note that this method is not always accurate.
- 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 run at startup. You can also checking the menu bar for an indication of what programs are automatically started. However, remember that some programs that may be configured to run at startup 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:
- Click Start, and then click Run.
- In Open type, Msinfo32.exe and then press ENTER.
- A comprehensive list of every program that is configured to run at startup is displayed. Check the Event log for errors that relate to any of these programs to see if there is one that is not working properly. If you find a related event, remove 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.
- You can view each component in your computer, including the drivers that are required to make the components work. To view the components that are installed on your computer, click the Components folder in the System Information console tree, and then click the sub-component to view its properties in the display pane.
- Check the Problem Devices folder in the System Information console under Components.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 that is associated with it.
- The PnP Device ID column lists device IDs such as PCI ID, ISA ID, an ID for some other bus type, or an unknown type.
- The Error Code column lists the error code that is associated with this specific problem. In many situations, the Device Manager error code helps you to 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 that is listed in the Setupapi.log file may help you to identify what may have created the unknown device. This is true if the device has a meaningful name. Sometimes the listed device name is 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 typically occurs when a partial Plug and Play ID is available, and Device Manager interprets it as a serial device. This interpretation can be caused by a compatible ID that is specified by the device. You can correct this by locating the startup program that may not be behaving properly.
Note that removing the unknown device in Device Manager works if a software program is creating the unknown device. You must remove the program that creates it, and then restart your computer. Also, if the unknown device is still listed after you restart your computer in Safe Mode, contact Microsoft Product Support Services for help with removing the device.back to the top Hardware Devices
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.
- Verify that 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:
Not Digitally Signed Note that a device driver that has been digitally signed might still be listed as an unknown device in Device Manager. Also note that you may not see this error message if it has been turned off.
You can block the installation of unsigned device drivers. This may be useful with mission-critical servers to prevent deliberate attempts to destabilize the server. To prevent the installation of unsigned device drivers:
- Click Start, click Control Panel, and then click System.
- On the Hardware tab, click Driver Signing, and then click to select the Block - Never install unsigned driver software check box.
- Click OK, and then click OK.
To view a list of loaded devices that are not digitally signed, use either of the following methods:
- View the Setupapi.log file for entries like the following entries:
The file (D:\WINDOWS\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:\WINDOWS\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.
- Use the Sigverif.exe tool to create a log file that lists all the unsigned drivers that are installed on your computer. The Sigverif.txt log file that is created by the Sigverif.exe tool is located in the %SystemRoot% folder. You can view this file by using a text editor such as Notepad. To run the Sigverif.exe tool:
- 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.
- You may experience a delay while your computer compiles a comprehensive list of unsigned drivers. Check the list of unsigned drivers, and then see if the driver manufacturer has an updated driver that is digitally signed.
USB devices that are based on earlier versions of the USB specification may create ghost devices that appear when the device is connected, and then disappear when the device is disconnected. Also, the device may work correctly, but may create a disassociated unknown device. This situation is typically caused by either outdated or mis-configured 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. Plug and Play devices are not typically listed when you manually install devices by 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 frequently solves this issue.
The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.back to the top