I have a laptop IDE to desktop IDE adapter, but it isn't obvious which way around to plug the laptop hard disk drive in. Which end does the power go in?
A laptop IDE drive has two groups of pins; a group of 43 pins and a group of 4 pins. (The group of 4 pins is unused.) The power connects at the end opposite to the group of 4 pins.
You should also check that the missing 44th pin on the laptop pins is on the same side (i.e., top or bottom) as the missing 44th pin on the adapter's pins.
If the adapter came with an instruction manual you should of course follow that.