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 hard to determine the cause of this unknown device, because there are few indications of what generates it.

Driver Magician helps you detect unknown devices easily and quickly. Its database contains hardware identities of about 20,000 devices. You can also find download link of unknown devices drivers with update function of Driver Magician.

Click "Tool" menu and "Detect unknown devices" submenu, a window with function of detecting unknown devices appears. Wait for a while, a list of PCI, AGP, PCI-X and PCIe  devices in your computer with their corresponding class will show in the listview.

Click any device, and the detailed information about its chip and vendor will show in the textbox below it.