When you start Windows XP, one or more of the attached USB (Universal Serial Bus) devices may not work, even though you receive no error message.
NOTE: These USB devices may be attached directly to your computer's USB ports, or to an active (powered) USB hub.
This behavior will occur if any single USB device requires more power than is provided by the hub or port, or if you have too many USB devices attached.
To workaround this issue:
If a device has the option to run with or without AC power, use its' AC power adapter.
If the hub has the option to be active or passive, plug in its' AC power adapter.
If you are using a passive (unpowered) hub, buy an active (powered) hub.
Connect the most power intensive device directly to the USB host controller on the back your computer
To determine the most effective combination of connected devices:
1. Disconnect all the devices from the USB hub.
2. Restart Windows XP.
3. Connect the devices until you receive USB Power Exceeded.
4. Try all different permutations of device connections.