PC buyers' guide: Memory
If a fast processor speeds up your PC, a large bank of memory stops it from slowing down. Don't buy 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 later, 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 buyers' guide: Storage
Falling prices mean that even a budget PC should be able to include a one-terabyte (1TB) hard drive; more expensive systems may provide twice this capacity. A 1TB drive should be adequate for most users, but you can never have too much storage space: digital photos, video and music will quickly fill a reasonably sized drive.
Backing up your files to an portable hard drives or network storage is essential: 1TB is a lot of information to lose in one go if your drive should fail. Alternatively, consider mirroring a pair of internal drives, although noise levels will increase.
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).
In systems costing more than £1,000, a supplementary solid-state disk (SSD) is a must - with a minimum capacity of 60GB if you're running Windows 7.
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
Laptop and netbook manufacturers often omit an optical drive to increase portability. For a desktop PC there's no excuse. That said, don't base your purchasing decision on the DVD drive - it's a cheap upgrade.
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.
Most desktop PCs now come with full-HD (1920x1080-pixel) flat-panel displays, although the less you pay for your PC the smaller the screen tends to be. Aim for a 21.5in model with a budget PC, and around 25in with a system costing more than £1,000. Be advised that manufacturers often round up their figures for advertising purposes - a 21.5in screen becomes 22in, and a 23.6in screen becomes 24in, for example.
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.
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