In normal occasions when you plug a USB device, your Windows computer plays an indicative melody and displays the device in the Devices and Printers window. If on the other hand you see a “USB Device Not Recognized” pop-up message (or nothing happens at all) when you try to connect your device, you need to do a trial and error to find whatever is causing the problem.
First, the simplest fix: disconnect the USB device, then reconnect it. If the issue persists, disconnect the device, restart your computer and connect the device again. If that still hasn’t fixed the issue, try plugging the device into another USB port.
You might be able to fix your computer’s failure to recognize the device by finding an updated, working device driver. In most cases, Windows does install a compatible driver automatically, but you can also opt to install the driver manually. Most device manufacturers have drivers available for download on their websites.
Is it possible that your device is faulty? Confirm by plugging it into another computer. If this other computer also fails to recognize the USB device, then the device is indeed faulty. In that case, you might need to have it replaced or repaired.
What if the computer itself is the problem? Try connecting other USB devices and see if the computer can detect those. If computer didn’t detect any device, the drivers for your USB ports are probably malfunctioning and must be fixed. Before you proceed, it’s best that you create a System Restore point and close all applications. Go to Device Manager at the Control Panel. In the Device Manager window, expand the Universal Serial Bus controllers section, right-click each listing and select Uninstall. When you reboot your computer, Windows will automatically reinstall the USB port drivers.
Alternately, try using this diagnostic and repair tool by Microsoft for Windows XP, Vista and 7.