• The PC processor
• Intel processors
• AMD processors
• Dual processors and multi-core processors -- a dual-core CPU
• The motherboard
• Motherboards for AMD and Intel
• Interfaces
• Memory
• Graphics controller
• Hard drive
• PC case
• Monitors
• Sound cards
• Speaker systems
• Media centre PCs
• Questions to ask the retailer

Here's a brief breakdown of the processors on the market:

Intel processors

In July 2006, Intel introduced what is still, to this day, the fastest microprocessor architecture on the market -- Core 2. The Core 2 is available in three versions: Core 2 Duo, which is a dual-core CPU aimed at mainstream and performance PC users, Core 2 Quad, which is a quad-core PC aimed at performance PC users, and Core 2 Extreme, which is a quad-core CPU that's aimed at enthusiast PC users. We'll touch on what dual-core and quad-core mean later, but for now all you need to know is that Core 2 Duo CPUs cost $170-$400, while Core 2 Quad CPUs start from just over $700 and Core 2 Extreme CPUs start from over $1300.

All these CPUs are 64-bit capable, which means they'll run either 32- or 64-bit software, and all will work happily on motherboards that feature the latest Intel chipsets (X33 and X38), but knowing exactly which CPU to put into your new PC is no easy task. You don't want to be caught-out with older technology when a newer model can be purchased for a similar or even lower price.

Let's start off with the basics: the clock speed of Core 2 CPUs start at 1.86GHz and goes right up to 3GHz for the high-end models. As mentioned previously, CPUs with higher-numbered model names won't always have faster clock speeds than their lower-numbered brethren, and here is where you really need to do your homework. For example, the Core 2 E4600 actually has a 2.4GHz clock speed, while the E6320 has a 1.86GHz clock speed.

The differences between these two CPUs lie in the cache size and the bus speed. The cache is high-speed memory that's built-in to the CPU. It's used for storing regularly used data and can really speed up the performance of a PC. The front side bus is the connection between the CPU and the motherboard chipset and memory. The higher the number, the faster your CPU will be able to transfer data between itself and the memory.

The E6x20 series CPUs have a 4MB cache and a 1066MHz bus speed, while the E4xxx series CPUs have a 2MB cache and an 800MHz front side bus speed. Furthermore, E6x50 series CPUs have a 4MB cache, but a 1333MHz front side bus speed.

All the E series CPUs are dual-core CPUs, which means there are actually two CPUs within the same physical package. This has its advantages when multitasking. You'll be able to work on at least two applications simultaneously without noticing a slow down in performance. The Core 2 Quad series (Qxxxx) and Extreme series (QXxxxx) CPUs all boast four CPUs within the same physical package, which allow for even more multitasking to be undertaken.

The Celeron is Intel's low cost CPU. It's not as powerful as the Core 2, but it's an adequate model for basic Web browsing and working on office applications.

So bear all these things in mind when you're purchasing your new PC so that you can get the most processing power for your money.

AMD processors

The latest CPU line from AMD is the Phenom. This CPU exists in tri-core and quad-core iterations (prices start at around $330) and it's aimed at all users and enthusiasts who are looking for plenty of power. The Athlon 64 X2 dual-core CPU is still around, and it has come down in price a lot -- you can find it for less than $120. The Sempron is even cheaper -- you can buy one from around $50 -- and it's a decent proposition for any low cost PC that will be used for word processing and Web surfing.

All these CPUs are capable of processing 64-bit software as well as 32-bit, and unlike Intel, AMD's CPUs are fairly straightforward to compare. AMD's CPUs are differentiated by model numbers rather than clock speed, but CPUs with higher model numbers will also have higher clock speeds than CPUs with lower model numbers.

The only difference is that AMD has regular and low power versions of its CPUs. Athlon 64 X2 CPUs with 'LV' in their model name will consume 65W of electricity, while Athlon 64 X2 CPUs with 'BE' in their model name will consume 45W of electricity. Sempron CPUs with an 'LE' in their model name will also consume 45W. Go for a low power version if you want your PC to run cool and quiet.

A special chipset isn't required to run any of these CPUs; any motherboard with an AM2 or AM2+ CPU slot will be able to accommodate any of these CPUs, but motherboards with the latest chipset (the AMD 790FX) will obviously offer the best performance. Note that Phenom CPUs might not run on older motherboards unless a BIOS update is performed. Don't buy a PC with a Socket 939 CPU as this is old technology and won't easily accommodate future upgrades.

Another type of Athlon 64 X2 CPU is available for enthusiast users -- Black Edition. CPUs with the Black Edition moniker are ones that can be overclocked more easily than non-Black Edition CPUs. If you're after a PC that you want to tinker with and get the most out of, then a Black Edition CPU is a good choice.

All Athlon 64 X2 CPUs are dual-core CPUs, while the Sempron is a single-core CPU. The Phenom can be found in three- or quad-core models. The Athlon 64 X2 models can have either 512KB or 1MB of cache per core, but, as they have an integrated DDR2 memory controller, they don't rely on a front side bus speed.

Dual processors and multi-core processors -- a dual-core CPU

Dual-processor motherboards are usually only found in server setups and high-end desktop PCs that use the functionality for intense graphics CAD and design work. Therefore, dual-processor boards aren't really applicable to the consumer desktop PC market. However, the recent introduction of dual-core processors by both Intel and AMD is bringing multiprocessing to the masses.

A dual-processor system is exactly what the name implies -- a system with two processors. You need a motherboard with two processor sockets to make this work (and such motherboards tend to be expensive). However, a dual-core processor is a little different. A dual-core processor is a single chip that has multiple processing "cores" in it. It will appear to the operating system as two processors, act the way two processors would act and have the same kinds of advantages as a dual-processor system has. It is only one chip, however, and only requires a single standard socket on the motherboard. Likewise, a quad-core processor has four processing "cores" in it.

Dual-core processors are currently the industry standard and are offered by Intel in its Core 2 range, and by AMD in its Athlon 64 X2 range. Quad-core processors can also be found in the Core 2 range, and in AMD's Phenom range. Most motherboards can accommodate either dual-core or quad-core processors by default, but a BIOS update might be required in order to properly identify the model name and speed.