From memory of the research I did waay back when I was trying to get my pc to hibernate, there are only three things which are required for a computer to be able to hibernate.
1) Correct Graphics Card Drivers
2) Correct WDM Audio Card Drivers (the old 9x style VXD drivers wouldnt allow hibernation)
3) Sufficient Disk Space to store the RAM Context
And that was it, with XP and 2000 both use WDM Audio Drivers so it gets down to having the right Graphics and Audio drivers and enough disk space.
Also with hibernation it does use no power at all. I did on a few occasions hibernate my pc, then disconnect it from all devices and electric, then store it for a few weeks and reconnect everything and continue using the pc. Standby on the other hand will fail if the power is removed as the power is required to keep the RAM alive.