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How to troubleshoot unknown devices that are listed in Device Manager in Windows XP
How to troubleshoot unknown devices that
are listed in Device Manager in Windows XP
Applies to: Microsoft Windows XP Home Edition, Microsoft Windows XP Professional, Microsoft
Windows XP Professional x64 Edition
For a Microsoft Windows 2000 version of this article, see 244601 .
INTRODUCTION
Device Manager displays a list of all devices that are installed on a Windows
XP-based computer. When you view device information in Device Manager,
you may see a device listed as Unknown Device next to a yellow question
mark. It may be difficult to determine the cause of this unknown device,
because there are few indications of what generates it. This article discusses
the possible reasons that an unknown device may appear in Device Manager.
More Information
The main reason for Unknown Device to display in your Device Manager is
because you have a device that is not working correctly. To fix this issue,
obtain an updated driver for the device.
Use the following methods to enable Windows to recognize your device.
Method 1: Windows Update
Visit the following Microsoft Web site to see whether the Web site autodetects
an updated driver for your device. Install all recommended drivers.
http://www.windowsupdate.com
Method 2: Download and install the latest driver from the Internet
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When you download a driver from the Internet, download the Windows XP
version of the driver when multiple Windows versions are listed. Use one of
the following options:
Visit the Web site of the computer manufacturer if the device came
with the computer.
Visit the Web site of the device manufacturer if the device was
installed after you purchased your computer.
Visit the Web site of the device manufacturer if the device was
preinstalled on your computer and the computer manufacturer
does not have an updated driver.
Look for a Drivers section or a Download section on the manufacturer’s Web
site, and search for the device name. Download and install the Windows XP
version of the driver.
Advanced user section
This section is intended for advanced computer users. If you are not
comfortable with advanced troubleshooting, you might want to ask someone
for help or contact support. For information about how to do this, visit the
following Microsoft Web site:
http://support.microsoft.com/contactus
Causes of unknown devices in Device Manager
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 Device and puts it in the Other devices branch. 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 function correctly without
additional device drivers because they are configured by the drivers
that are included with Windows for these bus types. However, an
additional device driver is needed if the device does not fit the
defined and supplied Windows class drivers. If the bus cannot
identify the device, it interprets the device as a composite device
and then reports it as such in Device Manager.
You are using a Microsoft Windows 98 or Microsoft Windows 95
Device Driver: You cannot use virtual device driver (.vxd) files that
are common to Windows 98 or to Windows 95 drivers in Windows
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XP. If you try to install them on your Windows XP-based computer,
the device may be listed as unknown in Device Manager. This
typically occurs when the device driver manufacturer does not
correctly differentiate between the two drivers or assumes that
Windows XP can use Windows 98 or Windows 95 .vxd files.
Unrecognized Device ID: Every hardware device has a special
identifier that is used by Plug and Play. This identifier can include
several 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 XP-based computer does not recognize the device
ID, Device Manager may list the device as unknown.
Note Software programs that require virtual hooks into hardware
may create these devices. Additionally, devices that bridge between
bus types, such as a device driver that enables a parallel port device
to emulate a SCSI or an AT Attachment Packet Interface (ATAPI)
bus, are also known to generate an unknown-device response in
Device Manager.
Faulty Hardware or Firmware: Faulty hardware or firmware may
cause a device to be displayed as Unknown Device in Device
Manager. 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. Be aware that software
installed by other methods may not be completely removed when
the device is removed in Device Manager. Therefore, you may have
to check the registry to verify that all entries are removed.
Troubleshooting for advanced users
Troubleshooting software issues
Use any of the following methods to determine whether an unknown device is
being created by software:
Start your computer in safe mode
Although not 100-percent reliable, starting your computer in safe
mode can be one of the easiest ways to determine whether the
unknown device is created by software.
To start your computer in safe mode, press F8 after you restart your
computer. On the Windows Advanced Option Menu that appears,
use the ARROW keys to select Safe Mode, and then press ENTER. If
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How to troubleshoot unknown devices that are listed in Device Manager in Windows XP
the unknown device is no longer listed in Device Manager, it is
likely that the unknown device is not hardware.
Check the Startup folder
If you suspect that a particular program is the cause of the
unknown device, check the Startup folder on your computer to see
which programs are configured to start when your computer starts.
The Startup folder is in the following location on your hard disk,
where C is the drive on which Windows is installed, and user profile
is your user profile:
C:\Documents and Settings\user profile\Start Menu\Programs
Use the System Information tool
The System Information tool can be useful when you have to
determine the cause of an unknown device.
To use the System Information tool to view a list of programs that
start when your computer starts, follow these steps:
1. Click Start, click Run, type msinfo32, and then click OK.
2. Expand Software Environment, and then double-click Startup
Programs.
A list of the programs that are configured to start when your
computer starts is displayed.
Check the event log for errors that refer to any of these
programs. If you find an event that is related to a program in
this list, remove the program. Be aware that when a program
creates an unknown device, it is not necessarily an indication
that the program does not work, unless the program depends
on that device to start.
To use the System Information tool to view a list of problem
devices, follow these steps:
1. Click Start, click Run, type msinfo32, and then click OK.
2. Expand Components, and then double-click Problem Devices.
A list of the devices that are installed on your computer that
may have a problem is displayed in the details pane, as
follows:
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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, 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. Frequently,
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 under Problem Devices, depending on the
device type:
PCI PnP Device ID:
Device Name |
PCI\VEN_00000&DEV_0000&SUBSYS_00
000000&REV_00\0&0000 | Error code
ISA PnP ID:
Device Name | ?\PNP0000\0
Bad or Incompatible Device Driver:
Device Name | ROOT\UNKNOWN\0000
View the Setupapi.log file
If the device has a meaningful name, use the information in the
Setupapi.log file to determine the cause of an unknown device. By
default, the Setupapi.log file is located in the %SystemRoot%
folder.
Sometimes the listed device name 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 typically occurs when
a partial Plug and Play ID is available, and Device Manager
interprets it as a serial device. This interpretation may 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 correctly.
Be aware that merely removing the unknown device in Device
Manager does not work if a software program is the cause of the
unknown device. You must remove the program and then restart
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How to troubleshoot unknown devices that are listed in Device Manager in Windows XP
your computer. If the unknown device is still listed in Device
Manager after you restart your computer in safe mode, contact
Microsoft Customer Support Services for help in removing the
device.
Troubleshooting hardware issues
To determine the cause of an unknown device, use one of the following
methods:
Remove hardware devices from your computer
Remove hardware devices one at a time until the unknown device
is no longer listed in Device Manager. Be aware that this method
may be time-consuming and is not always reliable.
Determine whether the device driver is digitally signed
When you install a device driver, and Windows detects that it is not
digitally signed, you may receive a warning message and the
option to cancel or continue the installation This message is
displayed only if your computer is configured to display a warning
message whenever an installation program tries to install a device
driver without a digital signature.
Note A device driver that is digitally signed can still be listed as an
unknown device in Device Manager.
For more information about driver signing for Windows, visit the
following Microsoft Web site:
http://www.microsoft.com/whdc/devtools/ddk/default.mspx
You can block the installation of device drivers that do not contain a digital
signature. Use this approach when you want to prevent any deliberate
attempts to destabilize the computer. To do this, follow these steps:
1. Click Start, click Run, type control sysdm.cpl in the Open box, and then
click OK.
2. Click the Hardware tab.
3. Under Drivers, click Driver Signing, and then click Block - Never install
unsigned driver software.
4. Click OK two times.
To view a list of device drivers installed on your computer that are not digitally
signed, use either of the following methods:
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View the Setupapi.log file
Look for entries that resemble the following:
The file (C:\Windows\inf\ntapm.inf) is not digitally signed,
ignoring driver date.
Installing section epatapi_inst from C:\documents and
settings\user name\my documents\parallel port test
drivers\epatapnt.inf
An unsigned or incorrectly signed driver (C:\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 C:\documents and settings\user name\my
documents\parallel port test drivers\epatapnt.mpd to
C:\Windows\System32\DRIVERS\epatapnt.mpd.
An unsigned or incorrectly signed driver (C:\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 File Signature Verification tool
The File Signature Verification tool lists all the unsigned drivers that
are installed on your computer. It creates a Sigverif.txt log that is
located in the %SystemRoot% folder. Use any text editor (for
example, Notepad) to view the file. To use the File Signature
Verification tool to display a list of drivers that are not digitally
signed, follow these steps:
1. Click Start, click Run, type sigverif, and then click OK.
2. Click Advanced, click the Search tab, and then click Look for
other files that are not digitally signed.
3. Click to select the Include subfolders check box, and then
click Browse.
4. Locate and select the %SystemRoot%\System32\Drivers
folder, click OK two times, and then click Start.
Review the list, and then contact the driver manufacturer for
information about how to obtain 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 fine,
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but may create a disassociated unknown device. This is typically caused by
firmware that is either outdated or configured incorrectly. In this case, contact
the device manufacturer for updated firmware.
A ghosted device can appear if you manually install a driver for a Plug and
Play device that the computer has already detected and installed. You can
resolve this issue by deleting the ghosted device.
Similar problems and resolutions for advanced users
For more information about how to use Device Manager to manage devices in
Windows XP, click the following article numbers to view the articles in the
Microsoft Knowledge Base:
283658 How to manage devices in Windows XP
307970 How to configure devices by using Device Manager in Windows
XP
304514 How to configure Device Manager to display detailed information
310126 Troubleshooting device conflicts with Device Manager
283361 Device Manager still lists a device after you try to remove it
310123 Explanation of error codes generated by Device Manager in
Microsoft Windows XP Professional
For more information about the System Information tool, click the following
article numbers to view the articles in the Microsoft Knowledge Base:
308549 Description of Windows XP System Information (Msinfo32.exe)
tool
300887 How to use System Information (MSINFO32) switches
For more information about how to troubleshoot with the Msconfig tool, click
the following article numbers to view the articles in the Microsoft Knowledge
Base:
https://support.microsoft.com/en-za/help/314464/how-to-troubleshoot-unknown-devices-that-are-listed-in-device-manager
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How to troubleshoot unknown devices that are listed in Device Manager in Windows XP
310560 How to troubleshoot configuration errors by using the System
Configuration utility in Windows XP
If the articles listed here do not help you resolve the problem or if you
experience symptoms that differ from those that are described in this article,
search the Microsoft Knowledge Base for more information. To search the
Microsoft Knowledge Base, visit the following Microsoft Web site:
http://support.microsoft.com
Then, type the text of the error message that you receive, or type a description
of the problem in the Search Support (KB) field.
The third-party products that this article discusses are manufactured by
companies that are independent of Microsoft. Microsoft makes no warranty,
implied or otherwise, about the performance or reliability of these products.
Last Updated: 17 Apr 2018
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