There are several ways to shutdown the XO, that is to halt the running software. This page clarifies some of the differences.
 Power Button
If neither of the above methods work, perhaps your XO is "stuck".
You can power off the machine by holding down the power button for several seconds until the power LED turns off or stops blinking.
This should force the XO to shutdown.
If none of the above methods work, the last method is to remove all power; take out the main battery and disconnect the external power cable.
 How do I know it is Shutdown?
To know that an XO is shutdown, you must check that the power LED is off, and not blinking.
The following indications show an XO is not shutdown:
- there is sound coming from the speakers,
- the display backlight is on,
- the wireless LED is on or flashing,
- the power LED is on or flashing.
The following indications have nothing to do with whether the XO is running or shutdown:
- the battery LED is on (it will remain on only because an external power cable is attached),
- you can ping the IP address from the network (another system may have the same IP address).