How to build your own PC

Graphics
While the Intel-integrated graphics present on our Asus motherboard provides adequate graphics power for 2D applications and DVD playback, itís incapable of running the latest computer games and canít play back Blu-ray movies. This is where a graphics card comes in.

Modern graphics cards have many little brains, called stream processors, and the more a graphics card has, the faster it is. However, the stream processors from the two biggest graphics card manufacturers, Nvidia and ATI, arenít directly comparable. This is because one Nvidia stream processor is more capable than one ATI stream processor, so ATI graphics cards use more stream processors to compensate.

The amount of memory graphics cards have is not as important as the graphics processing unit (GPU) being used, but 512MB memory will still give a boost over 256MB in games.

Obsessive gamers playing on monitors with very high resolutions (1,920x1,200 pixels and above) benefit from SLI (for Nvidia cards) or Crossfire (for ATI cards) configurations, where two, three or four graphics cards are combined to offer improved performance. Only top motherboards and power supply units (PSUs) support such configurations and the high cost of these setups make them inappropriate for most PCs.

We're going to use an Asus EAH2600XT, which is a workaday graphics card with 256MB of Ram.

A case to hold it all
Choosing a case is often a purely aesthetic choice. Small and understated cases can be suitable for living rooms, while teenage boys may clamour for big gaming cases with see-through panels and flashing lights.

Either way, make sure to choose one to fit the motherboard - we're using an mATX motherboard so a larger ATX case will be fine - and remember to note how many drive bays you need. For a PC with two optical drives and two hard disks, the case must have two 5.25in drive bays and two 3.5in drive bays. Many cases come with USB and Firewire ports on the front, which improve accessibility.

We're going to use an Antec Sonata 3 case, which uses sound-dampening technology to keep the noise down.

Power supply
The power supply unit (PSU) provides energy to each individual component in a PC. The factors to consider when choosing a PSU are wattage and efficiency. The wattage states the peak theoretical power output a PSU can provide, but this figure can be overstated. A typical PC will have a peak power draw of 150w. Office PCs with integrated graphics can draw as little as 40w, while gaming PCs with many graphics cards can draw up to 400w.

Another figure, PSU efficiency, determines how much electricity is wasted when the PC is turned on. A computer that draws 130w using a power supply that is only 70 per cent efficient will cost more to run than a PC drawing the same power from an 80-per-cent-efficient PSU.

The case we're using comes with a 500w PSU with an ë80plusí sticker on it: this indicates it is over 80 per cent efficient, the highest standard around.

For PCs with an add-in graphics card, make sure the PSU has the right connectors for it. High-end graphics card need either one or two 6-pin PCI Express power adapters and some need an 8-pin plug. Also research how much power the graphics card manufacturer thinks the PC will need.

Peripherals and finishing touches
All modern motherboards come with a built-in Ethernet port for network and internet connectivity. However, if the router sits far away from a PC, it can be useful to adopt a wireless network. We're going to add a Wifi card to our PC ñ but this is not an essential item.

With this in place, there will be one free PCI Express x1 slot left on our motherboard, into which we'll insert a tuner card to watch and record digital terrestrial TV. Again, this is not an essential item.

That is the essence of the PC complete, but we still need a keyboard and mouse. Some, notably older ones and some special gaming devices, require the motherboard to have PS2 ports; though almost all modern input devices will connect via USB.

There's also the operating system to consider. Most users are comfortable with Windows, and we think Windows Vista Home Premium is the most affordable and appropriate version for home users. Ubuntu Linux is the most popular free operating system, and can be downloaded at no cost from Ubuntu.

Finally, it's worth buying an anti-static wrist-strap (just a few pounds from any electronics shop) and for the build youíll also need a cross-head screwdriver.

Get ready to build
We've covered the major parts that make up a PC and you're welcome to use the same or similar components. However, we canít guarantee the PC will be fit for your purposes: you must make your own buying decisions.

Popular internet retailers will offer the best prices for the components we have discussed. As a starting point, log on to Computeractive's own price-comparison site. So, with all the parts ordered, it's time to get building.