Motherboard, expansion discs and memory: Discover what’s inside your PC

Upgrading a PC is a straightforward task, but it does depend upon some skill with a screwdriver and some familiarity with its hardware. Fortunately, it’s easy to see what’s inside a desktop PC by simply removing the case and taking look — a luxury that laptop owners, unfortunately, can’t enjoy.

Before you begin

Most desktop PCs have a case that can be opened by removing a few screws on the rear panel and a screwdriver usually isn’t required — just make sure that the PC is unplugged before you start.

It’s also worth investing in an anti-static wrist-strap (£2-6) before ventu

Disk drives and power

What you see inside a PC depends on how big the case is, how many components it has and how neatly it’s been assembled. At the very least, you should see one of more ‘drive cages’ behind the front panel that holds the CD/DVD and hard disk drives, with cables coming from the back of each — these may be wide or narrow, depending on the age of the PC.

The cables can be disconnected and the drives removed from the cages (usually after undoing some screws) if one needs to be replaced.

You’ll also see a large metal box at the back of the PC where the mains cable connects. This contains the power supply and several other cables emerge from this to connect to other parts of the PC — including the various disk drives at the front.

Even when the PC is unplugged, its power supply can still be dangerous, so while it’s safe to disconnect its cables from other parts of the PC, leave the power supply itself alone.

Expansion cards

Below the power supply you may see one or more ‘expansion cards’, or you may just see the empty expansion slots on the motherboard they plug into.

A graphics card is a type of expansion card (one with a large fan and/or metal heatsink, usually) and it’s held in place with a screw at the back of the PC’s case. The back edge of the graphics card pokes through a hole in the back of the PC’s case so that a monitor cable can connect to it.

Other expansion cards use a similar arrangement and you may see power cables from the power supply connecting to some of them.

The motherboard

Expansion cards plug into slots on the PC’s motherboard, which is the large circuit board that covers the bottom or side of the case. Disk drives and other components connect to this so that they can communicate with the rest of the PC, so don’t be surprised to see it covered with cables.

You may also see a large fan, usually with an elaborate heatsink, on one part of the motherboard — this is the cooling system for the processor that sits beneath it. In turn, the processor plugs into a square socket on the motherboard, although you probably won’t be able to see this under its fan.

Memory slots

Long, thin memory modules — ‘DIMMs’ — are also slotted into the motherboard. There are usually at least two slots and at least one will be occupied, although this depends on how much memory is installed. The slots have a small slip at each end to hold the memory module in place.


The back side of a motherboard also pokes through the back of the PC’s case to expose its various ports — USB, network and so on — although these are only visible from the outside. The back of the case also often has a large fan to suck warm air from the inside, keeping the PC cool, and there may also be one on the front to suck cool air in.

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