|Are your users connecting external USB devices then not unplugging them correctly?|
"Use Add/Remove Hardware (Windows 2000 only):
1. Plug a USB device in to one of your available USB ports
2. Go to Start>> Control Panel
3. Select Add/Remove Hardware
4. Select Uninstall/Unplug a device
5. Select the device that you would like to unplug/eject
6. Select Finish when done"