PC upgrades: Processor and motherboard
Intel's second generation of Core-series processors (aka 'Sandy Bridge') wipes the floor with all other chips in performance terms. Each processor includes an updated version of Intel's integrated graphics solution, providing accelerated graphics encoding and VGA and HDMI outputs. This means non-gamers can potentially save some cash by omitting a discrete graphics card, and will still be able to watch full-HD (1920x1080-pixel) video.
Several members of the Sandy Bridge processor family have been specifically designed for overclocking, denoted by a 'K' at the end of their product name. These chips are slightly more expensive than their non-K variants but are multiplier-unlocked, allowing for easy overclocking in the Bios. They demand a P67-chipset-based motherboard, however, which won't support the processor's integrated graphics. Also note that if you do wish to overclock your CPU, the standard processor cooler fitted by Intel may need to be upgraded, and you'll require at least a 750W-rated power supply unit (PSU).
For non-K Sandy Bridge processors, an H67-chipset-based motherboard is a cheaper alternative. These motherboards are not compatible with first-generation Core-series chips, so buying into the technology now will future-proof your PC.
The fastest processor in the new series is the 3.4GHz Core-i7-2600K. At 3.3GHz, the Core i5-2500K offers a slightly lower specification. It has no support for hyperthreading and 6MB rather than 8MB of level 3 cache. Both chips are also available in cheaper non-K versions that don’t offer the same overclocking potential.
Turbo Boost technology allows a processor to overclock a single core (or all four when used with a 'K' processor and a P67 motherboard) when the system is under load.
The more cores a processor has, the more able it is to multitask and run intensive multithreaded applications such as video editing. All the chips in the Sandy Bridge family are quad-core, as are the older Core i5-700-, -800- and -900-series CPUs. Of the older chips, dual-core processors such as the i5-600 series tend to have higher clock speeds, and thus will perform better when working with single-threaded applications. Single-core processors will be noticeably slower.
PC upgrades: Memory
If a fast processor speeds up your PC, a large bank of memory stops it from slowing down. Don't fit a Windows 7 PC with less than 2GB of system RAM. Most are fitted with at least 4GB, although we've seen £1,000-plus systems offering as much as 16GB. Sandy Bridge PCs should come with at least 8GB. For the PC to access more than 4GB of memory, and for systems running dual-graphics setups, you'll also need to be running a 64bit operating system.
Sandy Bridge processors and the Core i5-700- and 800-series chips require DDR3 RAM, while older chips can use less expensive DDR2. The triple-channel architecture of the Core i7-900-series processors requires you to install memory chips in threes (3GB or 6GB, for example), but Core i7-800- and -2000-series CPUs use a two-channel system. DDR3 memory is getting cheaper and bodes well for performance.
If you plan to upgrade the memory, check how many slots are free on the motherboard. If, for example, a PC vendor has installed four 1GB sticks of RAM, thus occupying all four of the motherboard's memory slots, an upgrade will be more expensive than if it had installed two 2GB sticks - in our example you would need to replace your existing memory rather than add to it.
PC upgrades: Storage
Adding a second hard drive is one of the simplest upgrades you can undertake. If you wish to do so internally, check the system case has a spare drive bay available. Some system cases offer a top-mounted SATA port for fast docking of a hard drive, while external drives can quickly and easily be added via USB.
For compatibility with the latest high-speed storage, check that the motherboard offers support for USB 3.0 and SATA 6 gigabits per second (Gbps).
Flash-based storage provides a noticeable boost to bootup times and system responsiveness. Solid-state drives remain expensive for now, but prices are starting to come down.
PC buyers' guide: Optical drives
Get a drive that can write to the DVD+/-R formats at 16-speed or better. If you want to get 8.5GB on to one disc, get a drive that can write to dual-layer discs at eight-speed (DVD+R DL).
Blu-ray drives are too expensive to be found in budget PCs, but where they are specified you'll also want a large full-HD (1920x1080-pixel) screen and a set of external speakers to complete the multimedia experience. PC vendors often offer DVD/Blu-ray combo drives; expect DVD speeds to be slower here.
PC buyers' guide: Display
The display is often overlooked by PC vendors wanting to curtail costs. However, it's the component you'll spend most of your time looking at, and is even more important if you do a lot of photo or video editing. Quality varies hugely among screens, and it's not only the size and resolution you need to consider. Also investigate viewing angles, whether the screen offers height, tilt and pivot adjustments, the pixel pitch, the response rate (8ms or below will minimise blur on fast-moving action), brightness and contrast. Where possible, it's a good idea to see the screen in person before you buy.
Aim for at least a 21.5in model. A 25in full-HD screen will not only provide a better experience when watching videos, playing games and working with spreadsheets than a 21.5in model, but it will also render text and icons slightly larger.
If you want to hook up a games console or projector, look for a screen with dual analogue and digital inputs. VGA is an analogue connection, while DVI, HDMI and DisplayPort are three types of digital connection.
Models with LED backlighting aren’t necessarily better, but can offer improved contrast, lower power consumption and a thinner, more desirable design.
PC upgrades: Graphics card
Decent graphics cards get cheaper all the time, and budget PCs can now handle games that were unthinkable a few months ago.
AMD’s ATI Radeon HD 5450 is a popular choice for a budget machine. It doesn’t offer a great speed advantage over Intel GMA integrated graphics, but it adds support for DirectX 11.0. If you really want to play games, nVidia’s GeForce GT 240 will provide some extra speed. Be prepared to lower your graphics settings to achieve smooth gameplay, however.
If gaming is important to you and you're prepared to spend a little more on your PC, look for an ATI Radeon HD 6870 or Geforce GTX 460. In a gamer-friendly system costing £1,000-plus, aim for an ATI Radeon HD 6970 or nVidia GeForce GTX 580.
nVidia cards offer support for realistic object interactions in games supporting PhysX and are able to display 3D content. Recent ATI cards can also be connected to multiple displays. Look out for pre-overclocked graphics cards, as well as those that come with custom cooling solutions.
Many nVidia and ATI graphics cards can be upgraded to dual-card setups later. To take advantage of this, your motherboard and power supply must be compatible. However, the current crop of motherboards which support the new Sandy Bridge processors have only limited support for multiple graphics cards, so buy the fastest single card you can afford. A single-card setup leaves more space for sound cards or TV tuners.
PC buyers' guide: Power supply unit
With no power-hungry components installed, a budget PC needs only a basic PSU. A 450W or 500W model is a good starting point.
For all other systems, the level of power you require will depend on the graphics card you want to use. Look for at least a 500W unit or 750W-plus if you plan to add another card or overclock the CPU.
Get a model with a full set of SATA and PCI Express connectors to make later upgrades easier.
PC buyers' guide: Sound
Most desktop PCs come with onboard sound rather than a separate sound cards, and budget machines tend to rely on the tinny speakers built into the monitor for playback. However, if you're buying a system with a large screen and a Blu-ray drive, you'll also want a decent set of external speakers. For the best playback, get a set that includes a subwoofer.