Troubleshooting unknown devices in Device Manager (Those with a yellow question mark)

Friday, June 29, 2007 19:59

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.

SOLUTION

Programs can also install virtual devices. Usually, these virtualdevices act as a bridge between the software and some hardwarefunction. Sometimes, device driver software for hardware isinstalled in a non-standard way. When the hardware along withdriver software is removed, all the entries in the Registry are not deleted.

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.