Colin Barnhorst said:
How many usb devices are attached to the computer? Even though your mass
storage device probably has its own power supply the usb bus itself may be
overloaded. Try the device without the hub. Disconnect as many usb
devices as you can while troubleshooting.
The USB bus system supports a total of 128 devices including the root port
and it's associated root hub. Every hub* and device counts, but there is a
limit of 5 hubs between the root port and the peripheral. The position is
complicated by the fact that a USB port on a modern PC actually connects to
one of 2 USB systems. USB1 (12 and 1.5 Mbps) peripherals and hubs connect
to one system while USB2 (400 Mbps) automatically connect to the other.
Although a USB1 system theoretically supports 128 devices, it is in fact
fairly easy to overload with just a modest handful of devices and when such
an overload occurs, there is no error message, just a device or devices that
won't work for any identifiable reason.
In your case you are getting a message saying that the device is not
recognised. This is usually a driver issue but can be caused by exceeding
the above limitations. First thing to try is to go into device manager and
find the actual device (it may be under unknown devices or under an obvious
heading (USB devices or disk drives) and may have a yellow '!' over it.
Right click and uninstall it. Ensure that any required drivers are
installed or available. Although not normally required for Windows XP there
are exceptions. Some drivers have to be installed before the device is
connected for the first time, others are installed after the device is
connected - check the documentation. Then connect your device to a root USB
port, ensuring that any power requirements are fully met. Once it works
here, it should work when connected anwhere alse (it will reinstall unless
it is electronically serial numbered).
If the device still won't install correctly, try it on another PC. It has
been known for conflicts to arise that prevent devices that otherwise should
work - not to work. These can be a PITA to resolve.
There is one gothcha. It sometimes happens that a second device of a
particular type won't work if an identical device is already connected.
This is due to manufacturers adopting the cheapest interpretation of the USB
specs (because of an ambiguity). There is a workaround, but I don't have it
to hand.
*Some hubs are actually 2 cascaded hubs, particularly if they have more than
4 downstream ports.
HTH.
