Installing a USB Serial Adapter on Mac OS X

Hi there,
I have followed all the instructions to install this driver, and despite the installation saying complete and successful, and my mac restarting, the driver is not evident

when I type the following

kextstat | grep prolific
ioreg -c IOSerialBSDClient | grep usb

nothing is displayed, and there is no USB-serial controller D displayed from the drop down on the network interface drop down !
please help !