DVD drive vs. hard disk

[MaxPower]

Does anyone have stats for power consumption of the hard drive vs. the DVD drive? I'd like to transfer some of my oft-watched movies to the hard drive (I have a spare ultra-bay drive) in my T60 to watch when I'm on the road but I wonder if battery life would be prolonged with the DVD drive instead.
Anyone compared the two?

[furrycute]

I read somewhere where someone did exactly that (I think it was in a computer magazine, but don't remember which one). Anyways, they found out that spinning the DVD definitely consumes less power than spinning the hard drive. So they recommended keeping the movie on the DVD.