Computer does not recognized external USB devices
The computer does not recognized an external USB devices is due to not correctly removing the USB devices. The right way to do remove an external USB device is to right click the USB icon in the System Tray and select "Safely Remove Hardware" feature. Another way is to go to the devices itself in My Computer, right click and select "Safely Remove". It people do not use this method, data can be lost or corrupt because the data have not finish written to the devices. Another result is that in the device manager.
1. Right click My Computer and select Properties
2. Click Device Manager in the left pane
3. Click View menu and select Show Hidden Devices
4. Look for Universal Serial Bus Controllers and expand it
5. You should see a ghost device of the USB or gray out device
6. Right click and select Uninstall
This is the result of not removing the external USB devices correctly. If you do it many times, it will be fully of ghost or gray out USB devicen. After a while, the computer will not recognized the USB devices. What you want to do is to delete all the ghost devices. Simply right click on what you want to remove and select delete. You can do it for other devices as well.
3. Click View menu and select Show Hidden Devices
4. Look for Universal Serial Bus Controllers and expand it
5. You should see a ghost device of the USB or gray out device
6. Right click and select Uninstall
This is the result of not removing the external USB devices correctly. If you do it many times, it will be fully of ghost or gray out USB devicen. After a while, the computer will not recognized the USB devices. What you want to do is to delete all the ghost devices. Simply right click on what you want to remove and select delete. You can do it for other devices as well.