StarCraft Walkthrough: 4: The Jacobs Installation
You have to retrieve the disks and save Raynor in this one. The disks are in the center of the screen; just keep your guys alive in the standard big-group-moves-together fashion, and you'll be ok! Watch for turrets - be prepared to target anything that pops up. Go diagonally northwest through two doors, zig zag your way up to the top of the screen. Teleport over to the top-right of the screen, and zig your way back into the exact center of the map. You don't even have to get back out, you just win right there.
StarCraft Walkthough Index