I think you will struggle to get it to wake over wifi.
It should wake on LAN though if connected to the router by Ethernet.
That's in the advanced power options. 

I recall similar annoyance but gave up trying as I do not like them connected by cable, as one of the reasons for changing the XP was it had been damaged by lightning through phone line and router via the ethernet cable.
As a common access drive I now have a 500GB portable drive plugged  in a USB on the (different) router.
This works pretty well really.