Greetings,
Disconnect all USB devices from your PC. Keyboard and/or mouse do not need to be removed. Does the unkn device remain? If no, you are missing a device driver for one of your connected devices. Some versions of Android require that you select the storage mode of the device when connected. You can plug each in to determine which is the problem.
If the unkn device remains after all devices are disconnected then a USB component is missing a device driver or one has failed to load.
Ways to resolve:
Right-Click on device, select update driver software, then Search Automatically for Updated Device Software. This will search windows update for missing drivers
Or, right click the device, select uninstall, do not check the box to remove driver software if prompted. Close device manager and restart. Device detection will occur when windows restarts.
Or, Device Manager > Right Click on device, select properties from the context menu. Now select the Details Tab, then use the Property drop down and change the option to Hardware ID. Search Google with the identifiers here and you may be able to narrow down what you are looking for. After, visit the manaufacturer's support page for the specific driver. Let us know if this helps.
