the ide channel will only support two ide decives hooked up and powered on at a single time.makeing your hdd external is just so it can be easy to switch your hard drive manually.the project 411 gb explained it pretty good i thought.you can have multiple devices hooked up to your ide wire but only two can be powered on at a single time.alls the switch does is divert the power from one over to the other.Thats what i got out of it anyway hooking up the switch is another story im not to good with electronics so i don't know all that talk about the multimeter and testing it ect.Has far has booting up i'm shure he probably has to have his C + E backup copied on each drive.