Windows XP can't boot from a hidden partition.
If you want to wake up XP from stand-by or hibernate it may be needed to enable some strange option in the power management of your network adapter.
Therefore open the device manager and right click on your network adapter and open the settings. Go to power management and activate all three options there.
I know this configuration says it would cause the opposite behavior but after many tests they are needed to get wake on LAN working on some systems.