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There are many reasons that a Device Manager will list a device asunknown and hence, there is no foolproof way to troubleshoot theerror. Some of the causes for Unknown Device error are:

• The hardware does not have the requisite software drivers, andWindows is not able to determine the device type
• The driver is not compatible with the OS and hence it is not ableto inform Windows about the hardware. This is common if aWindows 9x/ME driver is installed on Windows 2000/XP.
• Each hardware component should normally communicate a basic device ID to Windows. If the hardware does not have this device ID or Windows does not recognise the device ID of the hardware, then the device is listed as unknown.

• First, boot the computer into Safe Mode. If the device is nolonger listed in Device Manager, then most likely it was a virtualdevice driver.
• Next, check the programs loaded at systemstartup (Start > Programs > Startup). By trial and error, disableeach program till you identify the software that is causing thedevice to be unknown. Uninstall and reinstall the software.
• Ifthese steps do not work, or if you suspect that the problem ishardware-related, remove hardware devices from your computer one at a time until Device Manager no longer lists theunknown device. Or, if you know what hardware is causing theerror, verify that the hardware is working and that you have all the correct and updated drivers for the OS. Install the driversthrough the Add Hardware Wizard.

Code Meaning: (Not applicable to Windows XP) Windows stopped responding when it tried to start the device, and hence will never try to start this device again.
Recommended Resolution: Run the Update Driver Wizard and reinstall with an updated driver from the manufacturer.

Code Meaning: Two devices have been assigned the same I/O port, interrupt or DMA channel. This could be by the BIOS, by Windows, or both. Also, it could be that the BIOS has not allocated enough resources for the device.

Recommended Resolution: Disable one of the devices. (Windows 9x/ME: Double-click, select “Disable in this hardware profile” on the General tab of the property sheet; Windows 2000/XP: Rightclick and select Disable)

OR
Check the Resources tab to get details of the conflict. Refer to the hardware documentation and/or the manufacturer’s Web site for instructions on the correct values that need to be set manually. Clear the “Automatic Settings” checkbox, click the “Change Setting” button, and input the values.

AND/OR
Reconfigure the BIOS resource allocation if possible. Refer to the motherboard documentation along with the device documentation.

Code Meaning: (Not applicable to Windows XP) Windows did not detect the hardware.

Recommended Resolution: Verify that the hardware is working and that the physical installation is correct. Refer to the manufacturer’s documentation for specific installation instructions.

AND
Remove the device from Device Manager and reinstall it using the Add Hardware Wizard.

Code Meaning: The device cannot work properly until the system is restarted.

Recommended Resolution: Restart the computer.

Code Meaning: (Not applicable to Windows XP) The device is causing a resource conflict.

Recommended Resolution: Run msinfo32.exe to get more information on the conflict. Check the Resources tab to get details of the conflict. Refer to the hardware documentation and/or the manufacturer’s Web site for instructions on the correct values that need to be set manually. Clear the “Automatic Settings” checkbox, click the “Change Settings” button, and input the values.

Code Meaning: (Not applicable to Windows XP) Another device is using a resource that this device needs.

Recommended Resolution: Run msinfo32.exe to get more information on the conflict. Check the Resources tab to get details of the conflict. Refer to the hardware documentation and/or the manufacturer’s Web site for instructions on the correct values that need to be set manually. Clear the Automatic Settings checkbox, click the Change Setting button and input the values.

OR
Run the Update Driver Wizard and reinstall the driver or get an updated driver from the manufacturer.

AND/OR
Remove the device from Device Manager and reinstall it using Add Hardware Wizard.

Code Meaning: (Not applicable to Windows XP) The drivers need to be reinstalled.

Recommended Resolution: Run the Update Driver Wizard and reinstall the driver or get an updated driver from the manufacturer.

AND/OR
Remove the device from Device Manager and reinstall it using the Add Hardware Wizard.

Code Meaning: (Not applicable to Windows XP) Windows cannot load the basic device loader file that loads the device driver, or it is missing or corrupt, or a software value for the device is missing or corrupt.

Recommended Resolution: Run the Update Driver Wizard and reinstall the driver or get an updated driver from the manufacturer.

AND/OR
Remove the device from Device Manager and reinstall it using the Add Hardware Wizard.