Step 5: Remove the Shell
Remove the upper shell by taking the screws holding it out of the bottom of the PC. As you lift the shell off of the chassis, make certain that no part of it is still attached to the bottom of the case or to the motherboard. If it feels like you have to force it, that probably means either a screw is still in place or a clip remains to be unsnapped. Before continuing, back off and double-check your service manual to discover any well-hidden screws that may have eluded you.
Photograph: Charlie Nucci