USB Extension cables and Hubs by themselves usually aren't 'recognized' by your computer, as your computer is not even supposed to 'know' that they are there.
Do devices that you plug into your USB extension cable function properly? Also, do devices that you plug into your four port hub function properly? If they do not, the problem is that either your computer does not have a proper driver for the device, or your USB cable, hub, or device are damaged.