>>1
Generally, the 2.5" IDE drive in your laptop has horizontal pins, expressed as a black plastic connector or as golden pins sticking out.
There is an adapter that converts those pins into a flat, board-like connector. If this adapter is missing on the new drive, then see if the old drive has this adapter still on it. That sort of adapter is so small that people can mistake it for being part of the drive itself.
You should find a slim seam where the adapter's rear face meets the pin seating plate on the drive. Carefully (goddamn it, I do certainly mean CAREFULLY!) use a razor blade and wiggle it into that seam, to lever the adapter off the drive's pins. It shouldn't take much force to get that done ... and if you seem to be using too much force and nothing's happening, then STOP! Take the drives to a computer shop and seek their assistance.