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.
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.
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 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.
Start your computer in safe modeAlthough 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 folderIf 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:
Use the System Information toolThe 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:
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.
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:
View the Setupapi.log fileIf 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 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.
Remove hardware devices from your computerRemove 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 signedWhen 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:
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:
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, 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.
Unknown Device Identifier enables you to identify the yellow question mark labeled Unknown Devices in Device Manager. And reports you a detailed summary for the manufacturer name, OEM name, device type, device model and even the exact name of the unknown devices. With the collected information, you might contact your hardware manufacturer for support or search the Internet for the corresponding driver with a simple click. With this utility, you might immediately convert your unidentified unknown devices into identified known devices and find proper driver on the Internet and contact the hardware device manufacturer or vendor. Known devices recognized by Microsoft Windows will also be analyzed independent of the operating system.
Most of all however, it's useful for searching through your Device Manager for unknown devices and extracting information from it. This is also useful for anyone who needs to know the exact components they've got installed rather than just a general idea or having to open up your PC. You can run Unknown Devices from a CD or US stick too so it's a useful addition to any PC technician's toolbox especially if you're working on several PCs at once.
This option requires basic OS understanding.Select Your Operating System, download zipped files, and then proceed tomanually install them.Recommended if Unknown Device is the only driver on your PC you wish to update.
If you are like me and have the ibm thinkpad t43/p model and see the unknown device error mentioned above when you install windows 7 you'll need to do the following to clear it up and have it install the driver correctly. First you need the tpm driver.. (try here: -307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-58656) 2b1af7f3a8