How to troubleshoot unknown devices that are listed in Device Manager in Windows XP (314464)

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The following are the most common reasons that Device Manager may display a device as Unknown Device.

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 places 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 are designed to function properly without additional device drivers, because they are configured by the drivers 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 common to Windows 98 or Windows 95 drivers with Windows 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 properly 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 used by Plug and Play. This identifier can include 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 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 permits a parallel port device to emulate a Small Computer System Interface (SCSI) or AT Attachment Packet Interface (ATAPI) bus, are also known to generate an unknown-device response in Device Manager.

Faulty Hardware or Firmware

Possible scenarios where faulty hardware or firmware may cause a device to be displayed as Unknown Device in Device Manager include the following.

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 installed by other methods may not be completely removed when the device is removed in Device Manager, and therefore you may have to check the registry to verify that all entries are removed.

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 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 need to identify 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, and then click Run.
  2. In the Open box, type msinfo32, and then click OK.
  3. In the left pane, 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. Note 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, and then click Run.
  2. In the Open box, type msinfo32, and then click OK.
  3. In the left pane, expand Components, and then double-click Problem Devices.
     
     A list of the devices installed on your computer that may have a problem is displayed in the right pane, as follows:
     • 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 under Problem Devices, 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
• View the Setupapi.log file
  If the device has a meaningful name, use the information in the Setupapi.log file to identify the cause of an unknown device. The Setupapi.log file is, by default, 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 properly.
  
  Note 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 your computer. If the unknown device is still listed in Device Manager after you restart your computer in Safe mode, contact Microsoft Technical Support for help in removing the device.
  
  

Hardware Devices

It is less complex to isolate hardware devices than virtual devices. To identify the cause of an unknown device, use either 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. Note 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, browse to the following Microsoft Web site:

  http://www.microsoft.com/whdc/devtools/ddk/default.mspx

It is possible to 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 Device Manager, click Driver Signing, and then click Block - Never install unsigned driver software.
4. Click OK twice.

To view a list of device drivers installed on your computer that are not digitally signed, use either of the following methods:

• 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 of 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, and then click Run.
  2. In the Open box, type sigverif, and then click OK.
  3. Click Advanced, click the Search tab, and then click Look for other files that are not digitally signed.
  4. Click to select the Include subfolders check box, and then click Browse.
  5. Locate and select the %SystemRoot%\System32\Drivers folder, click OK twice, 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 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 just fine, but may create a disassociated unknown device, which is typically caused by either outdated or incorrectly configured firmware. 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.

For additional 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: For additional information about the System Information tool, click the following article numbers to view the articles in the Microsoft Knowledge Base: For additional information about how to troubleshoot with the Msconfig tool, click the following article numbers to view the articles in the Microsoft Knowledge Base: 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.