Does it work in another machine?
Somethings to try:-
Refresh USB Ports Use Drive clean up to remove USB device drive info from the registry http://www.uwe-sieber.de/files/drivecleanup.zip
In device manager Uninstall EVERYTHING under the heading USB, reboot the PC let XP find and install new hardware. Your equipment should now be recognised.
Remove all USB devices
Download and run USB device View
Uninstall ALL devices that are shown as not connected.
Reboot the machine.
Plug in your USB device and windows should then find new hardware and reinstall the drivers for the device.