New Plugable USB 2.0 does not work - unknown hardware

I have a new plugable USB 2.0 Multi-card Reader which does not work on any of my three computers - two Dell desktops with XP and a Toshiba laptop with Windows 7. On each one it says unknown hardware. I have followed the troubleshooting instructions to no avail. I need to replace an old card reader which is on its last leg. Any help would be most appreciated.