what speed is the usb device your plugging in....you might be plugging in a 2.0 into a 1.1 usb port but if this happens you will be prompt with a message saying usb not recognised because its the wrong usb port, on my laptop there's 3 usb ports, two 1.1 ports and one high speed 2.0 usb port, the problem is the usb ports are not marked, they only way to find out where the 2.0 port is, is by plugging in a 2.0 usb device until its recognised
go to device manager and see what speed the usb ports are