I've had this issue for over 2 months, after a full shutdown, during the night (between 3 & 7AM), if my HDD with Win 8 RP is plugged in, it turns itself on. This is the only OS that has ever done this to me. No one, other than myself, uses this desktop.
My notebook that has Win 8 RP, along with 7 Pro, doesn't do this.
Is anyone else having this experience, & the cause identified? One shouldn't have to remove their HDD at bedtime, or switch out to one with an earlier version, to prevent this.