Today's modern desktop PCs offer a wealth of options: You can go for a PC with a fixed retail configuration, or you can customise your system by stepping through a sometimes dizzying array of choices from a configure-to-order vendor. The resulting array of components is no longer wrapped up in a beige box, but in a colorful shell of highly variable shape and size, differentiated by indecipherable naming conventions.

Presented with so many possibilities, you need to narrow the field by considering what you want to use your new desktop for. Are you an avid photographer looking for a speedy but cost effective platform for editing high-resolution photos? If so, you'll benefit from buying a machine with extra RAM and a discrete graphics card. If you've acquired an extensive media collection, and want an inexpensive and compact way to pipe it to your HDTV, a compact PC tailored toward media sharing and playback may be your best bet.

Whatever your needs, you can find a desktop configuration to fit the bill.

Desktops fall into three major categories, each with its own range of price and performance: compact PCs, all-in-one PCs, and classic tower PCs (which we subdivide into budget, mainstream, and performance categories). Each style of machine has different strengths and weaknesses, and choosing the one that's best for you depends largely on how you plan to use it.

Once you've picked the appropriate desktop category, our guide to PC specifications will help you pick a machine that delivers the performance you need, while staying within your budget.

Compact PCs

As the smallest members of the desktop computer family, compact PCs often omit features to deliver computing power in a space saving package. The combination of energy efficient components, quiet operation, and small size makes compact PCs ideal for people who want a nonintrusive machine. A typical compact PC costs between £200 and £400, though the price goes up as you add upgrade options.

Compact PCs tend to be equipped with notebook or netbook components, such as Intel Atom processors. This limits their usefulness in tasks that demand lots of processing power, but it makes for quiet, energy efficient operation. Not all compact PCs are created equal, however, so pay attention to specifications when shopping. Some compact PCs are configured for as low a bottom-line price as possible; others are packed to the gills to deliver optimal performance in a compact system.

Acer Aspire Revo R3610 Most compact PCs rely on integrated graphics. In some cases (depending on the CPU and the integrated graphics chipset), anything more complicated than a Flash-based browser game will be unplayable, but you will be able to eke out competent media streaming with Intel integrated graphics. A machine toting nVidia's Ion platform, like the Acer Aspire Revo R3610, usually fares much better. Gaming still isn't an option, but 1080p video is, whether you stream from a larger PC or over the web.

When assessing smaller PCs, keep an eye on the ports. The smaller the footprint, the fewer features you can reasonably expect, and that includes fewer connectivity options. Though you'll get a VGA port and (on average) six USB 2.0 ports, many compact PCs also offer HDMI, an asset for home theatre setups. The typical hard drive size is 320GB, though 250GB is also common and we've seen compact system carrying up to 1TB (for a £70 upgrade premium).

All-in-One Desktops

All-in-One PCs are self-contained: components are mounted behind a display, with screen sizes ranging between 18- and 27-inches. With no cords to manage or peripherals to juggle, setting up your new all-in-one PC can be as simple as pulling the machine out of the box and plugging it in.

MSI Wind Top AE2010 With their compact size and integrated displays, all-in-one PCs can generally be placed wherever you've got a spare power outlet. Some all-in-ones also offer a rather distinct perk: touchscreens. With support for multitouch gestures worked into Microsoft's Windows 7, all-in-ones offer a clever way for users to interact with their media, while still getting a full-fledged PC.

Sony VAIO L117FX/B All-in-one components vary from brand to brand, but you can expect to pay more for an all-in-one than for a similarly equipped desktop. Again, some models target buyers on a tight budget, while others load up on performance-oriented system components (at a higher price, of course). For example, low-priced machines like the MSI Wind Top AE2220 use notebook or netbook processors and integrated graphics. You'll get reduced performance to match the reduced price tag. If you have a larger budget, you can opt for a model like the Sony VAIO L117FX/B, which includes a quad-core processor (most often seen on full-size desktops), to deliver superior performance, and offers a large 24-inch screen. You'll be paying in the area of £1800 for those high-end specs, however.

Many all-in-one PCs come with a wireless keyboard and mouse, Bluetooth support, and Wi-Fi connectivity. This reduces cable clutter to a minimum, an important consideration in spaces where an attractive décor or efficient use of space is at a premium.

Budget PCs

Acer Veriton X270 A budget tower desktop carries standard desktop components, but can cost as little as £200 if you select older hardware or inexpensive, low-end processors. Typically, these PCs are minitower systems, with fewer drive bays than a full tower has. The Acer Veriton X270, for example, offers an older Core 2 Duo processor but delivers relatively speedy performance for just £400. Beware models that come equipped with AMD Sempron or Intel Celeron processors, as those CPUs' performance drawbacks will cancel the advantage of their low cost.

Inexpensive tower desktops usually incorporate low-powered, integrated graphics rather than discrete graphics cards. As a result, your entertainment options may be limited. High-definition media playback suffers on models equipped with older Intel-based integrated graphics, and if you're interested in gaming, you'll be hard pressed to tackle anything more demanding than Flash-based offerings. Machines equipped with Intel's Core i3 processor build improved integrated graphics performance right onto the chip, though they still won't be adequate for video games, they will support satisfactory high-def media playback.

Budget PCs generally offer at least 320GB of storage space and at least 2GB of RAM, but permit few upgrade options beyond adding RAM or a larger hard drive. They rarely leave much room for expandability inside their cases, either. Still, if you need a machine for nothing more than word processing, email, and occasional DVDs or online videos, these machines should suit you just fine.

Mainstream PCs

Gateway FX6800-01e Higher up in the desktop chain, you'll find machines aimed at mainstream users. These PCs start in the vicinity of £600, and carry at least 500GB hard drives and about 4GB of RAM. Powered by dual-core and lower-end quad-core processors, they deliver better performance than budget desktops, without breaking the bank. Consider the Gateway FX6800-01e: For just over £900, this machine features a quad-core Core i7-920 processor, and an ATI Radeon HD 4850 graphics card.

Photo-editing applications stand to benefit from working with multicore processors, and entertainment enthusiasts will appreciate the improved gaming performance and stutter-free HD media playback that a discrete graphics card helps deliver. Many of the machines in this category include a Blu-ray drive, either standard or as an optional extra. And if your video editing needs are modest, you probably can find a machine in the mainstream price bracket that has enough power to handle your creative projects. 

Performance PCs

Maingear Shift Occupying the high end of the spectrum are performance desktops. Such PCs generally start at a little over £1300, with some outliers, like the Maingear Shift, hovering in the range of £5000. Most performance PCs are full tower systems, equipped with a slew of drive bays and expansion slots. Designed to tackle challenging tasks, they come equipped with the latest and greatest Intel and AMD dual- and quad-core processors, 6GB or 8GB of RAM, and at least one discrete graphics card. Some performance desktops include multiple graphics cards to deliver improved graphics performance.

Performance desktops are suitable for users who need a lot of processing power to get their work done, professionals who do extensive high-resolution photography or video editing, and gamers who are willing to pay for top-of-the-line visual effects.

Traditional PC manufacturers like HP and Dell sell performance machines, but so do smaller boutique PC makers that specialize in highly configurable custom machines, tailored to your needs and budget.