One of the best things about owning a PC is that if you're prepared to open the case up, you can upgrade your system any time you choose.

In addition, because it's a modular design you can concentrate on upgrading the oldest parts, or even add completely new functionality with the addition of a plug-in cards or USB devices.

The heart of this system is the motherboard, into which all your other PC components plug into and communicate with each other.

There's a great deal of choice when it comes to buying a new motherboard, from the type of CPU that it's compatible with, the memory it uses, the size, and even if it has extra functionality such as onboard audio and graphics.

One of the most important decisions about choosing a new motherboard is what processor you want to use, and your choice will dictate how the CPU fits into a socket on the motherboard.

Choice of two

Intel and AMD are the two processor manufacturers. Their ranges of CPUs use a completely different socket and furthermore each company changes the number of pins that their processors use from time to time, and so there are a number of different sockets to choose from.

Intel has even gone as far as removing the pins from its CPUs, replacing them with contact points and having the pins in the CPU socket instead, which helps to avoid the issue of bent pins that could occur when fitting or removing a CPU.

AMD has included some backwards compatibility in some of its sockets that, while helping some users to use newer or older CPUs in their motherboard, can cause some confusion.

If you're buying a new motherboard then there's a good chance that you'll be buying a new CPU too, unless you really want to keep using your old processor. If you're sticking with your old CPU then of course you'll need to buy a motherboard with a compatible socket.

Intel's most recent CPUs are known as Core i7 and Core i5. Core i3 is due to be released soon.

Slightly older, but still perfectly good CPUs are the Core 2 range; pick from either Core 2 Duo (dual-core) or Core 2 Quad. Core 2 CPUs use a socket design called LGA775.

Core i7 is a very high-end CPU and so Core i5 will be a more mainstream solution, while Core i3 includes an integrated graphics processor. All three of the Core i-series CPUs use the same socket 1156 format, so if you decide to purchase a Core i3 CPU it'll be possible to upgrade to a Core i7 CPU at a later date.

The Intel Celeron is aimed at the budget market, while the Pentium fills the gap between budget and dual-core.