Although it's possible to attach the power supply unit, or PSU, to components as they are inserted, it may be worth leaving that until last in the interest of tidiness - there are usually excess PSU cables that can be tucked neatly out of sight. The thickest plug coming from the PSU should be attached to the motherboard. A clip indicates which way round the power plug fits. Push down until the adapter clicks into place. The square four-hole block coming from the PSU provides power to the processor. It should be plugged into the motherboard socket near to
the processor.

It also has a clip indicating which way round it fits and it will also click when it fits into position. Both the hard disk and optical drive draw power from a Sata power adapter, two of which should sit on one PSU lead. If an add-in graphics card is being used, it may require a direct link to the PSU. Cheaper graphics cards usually have one six-pin power plug, while expensive graphics cards have two six-pin plugs that must be attached for the graphics card to operate correctly.



Case fans will have one of two types of adapter a larger four-pin connector or a smaller motherboard fan connector. The former is a slim rectangular adapter that draws power from the PSU. The latter connects directly to a connector labelled 'fan' on the motherboard itself. Modern PC cases have one fan at the front or side of the case to draw air in, and one at the rear to expel it. The temperature of the case can be monitored from within the Bios (which we'll explain later). If it is consistently over 40°C, it may be worth using additional case fans. However, fans increase noise levels and push up the energy bill.