Examine the box What is inside

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Inside the box

What is inside a typical computer 'box'?

From the front you should be able to identify:

	The CD/DVD drive. It often has a socket for a jack plug to let you listen.
	The hard disk might be evident but often there is just a light near a little symbol
	A 3 ½” disk drive used to be common but is now rare.

Laptops have similar outlets but they are arranged around the edge.

At the back

	A socket for the keyboard and the mouse.
	USB sockets to connect almost every type of device including Ipods.
	Video and audio outputs: the socket to match the lead from the screen should be identified. On most computers, the sockets and plugs are colour coded.
	Modem: you have a modem if you see a lead with a phone plus on it or a socket to receive such a lead.
	There will also be one or more parallel sockets for a printer with a similar-looking socket known as a serial port. This is the mysterious ‘COM’ port you will find if you had to connect your external equipment before the arrival of the USB.

Lifting the lid

It is vital that the power cable is disconnected before you start work. It is not only much safer, but much easier to carry out the inspection and cleaning if all cables are disconnected.

If you have a laptop, go no further. They are a modern miracle of close packing. If you take them apart, you will never put them together again. The components inside are not generic and cannot be switched, so there is no point in exploring the innards. (Some do allow for some of the moving devices to be exchanged but, if this is possible, you do not need to open the box to do this)

Check for seals. These might still be intact. The seal will tell you that if you break it the warranty is void. You should only be messing with the machine unless it is already years out of any warranty, so you can ignore this. If the seal is broken, it does not mean that the machine has already been repaired. It is very normal to open machines, even new ones, to fit extra bits inside. So it is not a bad sign if you find the seal is broken.

	You might find some notes written on the equipment or even a sticker inside telling you how things are configured.
	Lift the lid carefully as occasionally there are wires attached.
	Next check for any loose leads. There are probably a few of these (see below). It is also possible that you might find a few bits of loose plastic or screws. Keep these.

View of wire harnesses inside a computer

Getting to know the insides

The interior is dominated by cables.

	You might have to remove the cable ties to let you move these aside. If you have to cut these ties, do it with great care. You can use bag-ties when you reassemble the computer to tidy it up.
	There are many types of plug. The good news is that they only fit one socket so the chances of making mistakes when it is all put together are minimises.
	There are 2 types of cable: The flat, grey ribbon cables. These have plugs and sockets along their length. When these sockets are attached to the cable, they push little pins through the wire to make a connection. These are IDC, Internal Displacement Connectors. Do not try to remove the plug - Do not tug the cable but always lift the plug. These are often made to measure, so if you move things about, they might not fit. However, provision is almost always made for extra data drives. There is a thin red line down one edge of the cable. If you examine the plug or sockets attached to the cable, you will notice that they are not symmetrical. Look very closely and you will find a little bar which can only be put in one way. If you look even closer you should find some numbers moulded into the plastic. There are bundles of thicker, brightly coloured wires which normally lead back to the power supply. There are thin wires and thick wires. These are terminated in a range of plugs. There is a plug to match almost every lead.
	The power supply is easy to identify as it has all the coloured wires and the fan. It is located at the rear, usually at the top, and normally has an on/off switch. The give-away is the socket or sockets that will bring the electricity in. If there are 2 sockets, one is male, the other female. One is for the power supply cord and the second is for the display, but you can plug it into its own supply. The advantage of looping through the computer is that the computer might switch it on and off for you.
	There is a set of racks or some other structure to support the various drives. There are also special trays to support smaller disks. If you start switching disks about, you need to make sure that you can match them to the rack. The hardware bits exist but you might have to hunt about or improvise. There are bits of removable plastic at the front to allow new drives to be fitted. The rack and the front covers are of a standard size which provides a high degree of interchangeability.
	There are different types of disk mounted on these racks. Hard disks come in several shapes. Older ones tend to be larger and fit in one of the bays at the front. Smaller modern hard disks fit inside the ‘box’ and have a pair of thin wires leading to a little light on the front panel. This should flicker when the drive is fetching data. If the light does not go on and off, it is an indication that there might be something wrong with your computer. The physical size is no indication of the capacity of the disk. CD/DVD drives are easy to identify. They either have a drawer that comes out to receive your disk or a thin slot which ‘snatches’ any CD you present to it (assuming it is not already occupied). There are many variations on this theme, with CD writers and DVDs now common. They all perform the same function of reading and are physically interchangeable. However, just because it fits, does not mean that you can either read or write the disk. You need the various bits of matching software. Almost all computers before 2002 came equipped with a 3½” disk. This played a vital role in starting the computer if something went wrong. As reliability improved, disks were used to transfer data, but this role has now been taken over by email or USB sticks. For older machines, this disk is an important resource and should be kept.
	Do not assume that items that can be physically interchanged will work. Every device requires some software called drivers to enable the computer to communicate with it. Happily these can be found by trawling the Internet and general-purpose, or generic, drivers are now part of operating systems.

The electronics

The most obvious feature inside the box is the motherboard, although you might have to move the many cables aside to see it.

Protruding from the motherboard at right angles will be various cards.

One will be the video card. This will have the socket for the video output for the display and probably some audio sockets.

There will probably also be a board with the electronics to link the drives to the computer. This has pride of place because it has to accommodate so many of the flat data cables.

There might be another card with various outputs on it. Some computer manufacturers have brought down the cost by building these facilities onto the motherboard, so the absence of attached boards is not a cause for worry.

You will also find banks of memory chips. These are the RAM. They can, in theory, be swapped around. However, there are numerous compatibility issues, so think carefully if you plan to change them.

Interconnections
The boards above plug directly into the motherboard. There are several sizes of socket and all that is needed is to find one that matches the board. Apart from that, the physical location is not important. Each time the computer starts, it looks to see what is located where - it draws a map of the electronics for itself.

The drives need 2 sets of cables: