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
- The device does not have the correct device driver
- 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.
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 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
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
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
: 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 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
Faulty Hardware or Firmware
Scenarios of how damaged hardware or firmware might 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 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
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
- 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
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:
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
The file (D:\WINDOWS\inf\ntapm.inf) is not
digitally signed, ignoring driver date.
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
- 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
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
Article ID: 327756 - Last Review: December 3, 2007 - Revision: 7.4
- Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
- Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
- Microsoft Windows Server 2003, Standard Edition (32-bit x86)
- Microsoft Windows Server 2003, Web Edition
- Microsoft Windows Small Business Server 2003 Premium Edition
- Microsoft Windows Small Business Server 2003 Standard Edition
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