Method 1 - Unplug Computer
So how did I finally fix the problem? Well, if you are lucky, it's a super simple solution! Try this method first and if it works, you'll have saved a lot of time.
Simply unplug your computer from the power supply. Yes that is it! Note that this does not mean just turning off your computer using the power button because most modern computers don't actually turn off completely and the motherboard will still get power. This is useful sometimes if you want to remotely wake up a computer, etc.
The motherboard is where all of hardware of the computer connects to, including the USB ports. Sometimes the motherboard needs to be "rebooted" because things can go wrong, i.e. all or some
USB ports suddenly stop working. The small microprocessor on the motherboard will reload the drivers and your USB ports should hopefully be recognizing devices again.
So first turn off your computer using the
Shut Down option in Windows or pressing the power button and then UNPLUG the PC from the wall outlet. Let it sit for several minutes and then plug it back in.
Method 2 - Update Device Driver
If Windows is not able to recognize the device, you may also see in Device Manager that the device shows up as an "
Unknown Device". You can get to
Device Manager by clicking on
Start and typing in
devmgmt.msc or by going to Control Panel and clicking on
Device Manager.
In that case, you should right-click on
Unknown Device, click on
Properties, then the
Driver tab and then click
Update Driver.
If this doesn't work, you can also try to download the driver for your device from the manufacturer's website. If the USB device is just a
flash drive, then it's probably not a driver issue. However, if you are installing a USB printer, drawing pad, etc, then it might be worth downloading the driver for that specific device.
Method 3 - Restart & Disconnect USB Devices
The next thing you can try is to disconnect all
USB devices and then restart the machine. once you have restarted, try to connect the USB device that was causing the problem.
If that particular USB port doesn't recognize it, try another one. If the device is recognized by a different USB port, there could be a hardware problem with one of the USB ports. If no USB port recognizes the device, then keep reading because it's probably something else.
Method 4 - USB Root Hub
Another thing you can try is to open Device Manager, expand
USB Serial Bus Controllers, right-click on
USB Root Hub and then click on
Properties.
Click on the
Power Management tab and uncheck the
Allow the computer to turn off this device to save power box. If you have more than one USB Root Hub listed, you need to repeat these steps for each one.
Click OK and then
restart your computer. Try to reconnect the USB device and see if it is recognized. If not, go back to the power management tab for each one and check the box again. If it does recognize the device, then leave them unchecked.
Method 5 - Connect Directly to PC
A friend of mine ran into this issue and the cause ended up being his USB hub. He only had three USB ports on his computer, so he bought a hub where he could connect an additional 8 USB devices.
I guess this proved too much for his computer and it just started sporadically not recognizing various devices. After removing the hub and connecting the device directly to the computer, it worked just fine.
We haven't really been able to find any other solution to this problem other than reducing the number of items connected to the hub. Actually, one other solution worked, but it meant having to buy a
new USB hub with more power.
If you are having this problem with Windows 8 or Windows 8.1, then you might be in luck. Microsoft has
released a fix for
Windows 8 not detecting USB devices properly. Make sure to install this hotfix if running Windows 8.
Method 6 - USB Troubleshooter
If nothing has worked so far, you can download the
Windows USB Troubleshooter Fixit tool. It's a free tool that works with Windows XP,
Vista and 7.
You can either have the troubleshooter fix the problems for you or select the fixes yourself. I would just let it fix them for you since the choices can sometimes be confusing and technical for the novice user.
Method 7 - Update Generic USB Hub
If you are getting the
Unknown Device error in Device Manager, you can also try one other thing. Open Device Manager and then expand
Universal Serial Bus Controllers.
You should see at least one item called
Generic USB Hub. On some computers, you might see two, three or more of these. Right-click on the first one and choose
Update Driver Software.
When the update dialog pops up, choose
Browse my computer for driver software.
When the update dialog pops up, choose
Browse my computer for driver software.
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