Disassembling the PC

You should label all components as they come out of the PC. This is in case you forget where they go. Try placing a number on a sticky note on each component and on its corresponding connections for easy recall.

Boot up the PC and check that the PC is operational. This is fundamental, otherwise you won’t know whether the PC worked in the first place when you reassemble it!
Disconnect power from your PC.
Disconnect all cables at the back of the PC (use sticky notes if needed to remember where they go).
Identify how the PC case comes off. If you have a manual that came with the PC, this will tell you. If not, many cases are secured with screws, thumbscrews and others are simply secured using latches.
Remove the PC case.
Disconnect all cables that go to the motherboard including hard disk drive (HDD) and floppy disk drive (FDD), power, etc. Remember to label everything.
Remove the HDD, CD ROM, and FDD and any other storage device.
Remove all jumper-connected wires from the motherboard. For instance, HDD activity LED, Reset switch, power switch and so on. Remember to label everything.
Undo any screws securing the main board. Some boards will have around six or more small screws. Be careful not to damage any delicate components or to exert too much pressure on the board.
Remove the actual main board from the chassis. Be very careful when doing this. Try not to rub the board against any other metallic components or edges as this could scratch the system board causing damage to tiny printed circuitry. Place the board on a large anti-static bag (the bags motherboards come in) or a soft, packing foam sheet.
Remove the memory module from the main board.
Remove the CPU from the main board. Some CPUs are easily removed by simply lifting a lever and pulling the CPU out. However, some are held in place using very tight fittings.
Inspect all the components and identify each of them.