The Device Manager displays a list of all devices that are installed on a Windows 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.

Method 1: Windows Update:
Visit the following Microsoft Web site to see whether the Web site auto detects an updated driver for your device. Install all recommended drivers : Microsoft Windows Update

Method 2: Download & install the latest driver from the Internet:
* Check the computer manufacturer if the device came with the computer.
* Check the device manufacturer if the device was installed after you purchased your computer.
* Check 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.

But what if the above methods fail & the device manager still shows the yellow question mark next to the 'unknown device'

Follow these steps to get it sorted:

1) Open the Device Manager [Right click on My Computer > Manage > Computer Management > System Tools > Device Manager].

2) Right-click on the unidentified/unknown device & open properties. In this example it will not be an unknown device, but you'll get an idea.




3) In the properties, click the Details tab.

4) Select the device instance ID or hardware ID. In the example you'll see a long line with a lot of gibberish. What we are looking for are the codes for VEN and DEV. These stand for vendor and device. As you can see in the example, the vendor is 11D4 and the device is 1981.



5) Next, open the following website: PCI Vendor and Device Lists

In the Vendor Search bar, enter the vendor ID, so in this case 11D4, and hit search. You'll get a search result, click it. Next, hit Ctrl + F (or whatever triggers the search function in the browser you use) and put in the device ID which is 1981. Search for the device.

6) Once the unknown device is identified, it should be easy to find a working driver for XP or Vista for it. This is especially helpful when you want to downgrade your Vista notebook or PC to Windows XP.

There are some exceptions though, which might be worth mentioning. Quick-keys on notebooks usually do not have a standard device ID. Also some power-saving CPU functions will not show a vendor and device code. These will usually show up as ACPI device. Google will help you out though. If the device is listed as an ACPI\AWY0001, stop looking, there is no driver for that. Fortunately it is also not a critical component and your system will not explode if you don't install it.

There's one more 3rd party tool, Astra32 which is an ideal solution for providing comprehensive information about the configuration of your system. Not only does ASTRA32 provide a detailed analysis of your system it also offers diagnostics along with working modes & comes with some powerful unique features.

Hope this helps someone