> It sounds to me like it could be the actuator mechanism that moves the
> read/write heads, moving into a "parked" position. As this position is only
> used when the drive is off it could be that the shaft has got a bit 'sticky'
> in that position. I'd back up anything that's not easilly replaced and carry
> on as usual.

I've seen on many Seagate drives that sound with more than one
computer when going to power off state. Parking heads seem a bit
different because the motor isn't turned off, but that sound is like a
complete motor shutdown as normal.