Did you check your headset with other system or laptop? if yes, then there is no issue with ur logitech headset but if you found the same trouble then there is serious problem with your headset. if its unable to detect there might be the problem with the inbuilt driver or the firmware must have got damage. if its under warranty then replace it thats recommended solution instead of formatting your system & wasting your valuable time. However its working with other system then you need to check with USB drivers and USB port of your system. Its always recommended to connect USB Device on motherboard's base USB port.