I paid someone to install a new NEC USB 2.0 in my 3 year old Medion PC
(o/s XP with service pack 2), but when I subsequently attached a
Freecom external back-up drive (USB 2.0) and Epson scanner (USB 2.0)
via a D-Link powered external hub (USB 2.0), I got a message on screen
implying that they would only run at USB 1.1 speed.  Being puzzled by
this, I looked at my list of USB items in Device Manager, but saw no
sign of the new NEC USB 2.0 card.  Surely it should be listed here? As
it is not, does this indicate that either the card has not been
installed properly or, if it has, that it is faulty?  Any advice would
be most appreciated.

The items shown on my Device Manager USB list are as follows:

Generic USB Hub
Sis 7001 PCI to USB Host Controller
Sis 7001 PCI to USB Host Controller
USB Mass Storage Device
USB Root Hub
USB Root Hub
USB Root Hub
USB Root Hub
USB Root Hub
VIA Rev or later USB Universal Hub Controller
VIA Rev or later USB Universal Hub Controller
VIA USB Enhanced Hub Controller

Please note that my Epson printer is also plugged into the external
hub and it runs at 1.1 speed.

Plug a USB mouse (or other device) into your new USB card.  If the
mouse works, you know your USB controller is OK.

It looks that your ms xp recognize your Nec USB 2.0 as Sis 7001 - USB.
>Sis 7001 PCI to USB Host Controller
>Sis 7001 PCI to USB Host Controller
Try to remove all usb devices from Device Manager and restart system.
Remove all these (better is also disconnect all stuff):
Generic USB Hub
Sis 7001 PCI to USB Host Controller
Sis 7001 PCI to USB Host Controller
USB Mass Storage Device
USB Root Hub
USB Root Hub
USB Root Hub
USB Root Hub
USB Root Hub
VIA Rev or later USB Universal Hub Controller
VIA Rev or later USB Universal Hub Controller
VIA USB Enhanced Hub Controller

When system start, it should install correct drivers.

pinchas in the earlier note is on track... 
I wanted to add two things :
1) if a 1.1 device is attached that becomes the default speed
2) remove the splitter and attach the device (usb drive ) to the usb port
(reboot of course) and you should see it at 2.0 !

hope that helps

patz

Install the drivers from the included cd if you have any.

Many thanks for all your comments which I really appreciate,
especially as I am a novice.  My PC only came with 2 USB ports and
because I use one for my modem, I decided to use the other one for my
powered USB 2.0 external hub, which has 4 ports, which I use for my
USB 2.0 scanner, USB 2.0 40gb external drive and USB 1.1 printer.
Going on everything that you have all said, my system recognises the
existence of my recently installed USB 2.0 card (shown as 'Sis 7001
PCI to USB Host Controller' in Device Manager).  I also now understand
that when I attach my USB 1.1 printer to the external hub, the default
speed of the external hub becomes USB 1.1 by default.  Furthermore, I
now appreciate that when I do a full system back-up (using Norton
Ghost software), it would probably be advisable to attach the external
hard drive directly to the PC via the second USB port on the back of
the PC rather than through the external hub (at the moment a full
system back-up through the external hub takes approx 4 hours, but at
USB 2.0 speed, it would probably take a lot less time).