Overclocking used to be a dirty word, but with the two main desktop PC processor manufacturers now selling CPUs designed for speed-tweaking, it's now a tried-and-trusted upgrade. PC Advisor shows you how to overclock your PC's processor, graphics card and memory.

If you want the best possible performance from your computer, but you can't afford any hardware upgrades, we'll show you how to safely overclock your desktop PC's CPU, graphics-processing unit (GPU) and RAM. Be warned, however, that modifying such components could void your warranty (firms selling parts specifically for overclocking will have more lenient policies). No-one will replace equipment that has been physically damaged by overclocking, so you need to be comfortable taking your PC's life into your hands before you change anything.

Use system-monitoring software to keep track of your tweaks; we like the free CPU-Z. Thoroughly clean your PC's case and keep your components as cool as possible. Overclocking pushes your PC past its specified peak performance, and the extra power creates more heat; you may want to consider adding air-cooling equipment.

Overclock your PC's CPU

The advertised speed of your processor is calculated by multiplying the base clock rate by what's logically known as a multiplier. To get more performance from your CPU, you need to increase one of these two variables. Ideally, you'll have an unlocked CPU (Intel's ‘K' series and Extreme Edition, or AMD's Black Edition), which offer more multipliers to adjust. But you can also get extra oomph from standard processors.

We overclocked a multiplier-unlocked Intel Core i7-2600K CPU running at a base speed of 3.4GHz (this is the processor's base clock rate of 99.8MHz multiplied by 34). With K-series chips, you can easily modify the multiplier from the Performance settings in the Bios. Boot into the Bios, increase the CPU multiplier number by one (from 34 to 35 in this example), hit Save and boot into Windows. If the PC doesn't produce error messages or begin continuously restarting, you're on the right path.

Launch CPU-Z and look on the CPU tab to confirm that your settings have held. Check the number under ‘Core Speed and Multiplier'. This will fluctuate, depending non what your PC is doing at the time.

Run a benchmark utility to stress-test the configuration, such as Prime95's free Torture Test mode or LinX. By pushing your PC to its limits, you'll have an idea of your processor's maximum clock speed.

If your computer remains free of blue screens or sudden restarts after a few hours of number-crunching with one of these tools, you're probably in the clear. You can stick with the current overclocking settings, or try a slightly higher multiplier.

Overclock your PC's graphics card

Overclocking a modern graphics card is usually a simple case of turning up a few sliders in your GPU-configuration utility. First, download the latest drivers from the manufacturer's website. You can find the latest software for nVidia graphics cards here; for ATI (or AMD), click here. Basic overclocking controls for ATI cards are found on the Overdrive tab of the bundled Catalyst Control Center software; for an nVidia card, you'll need to download the nVidia System Tools utility.

Launch the utility for your card and locate the clock-speed controls for the GPU processor and memory. Check Catalyst Control Center's Overdrive tab, or the nVidia Performance menu. Raise the sliders in small increments of 5 to 10MHz. Each time, save the change, reboot the PC and stress-test the configuration by running the free Heaven 2.0 or playing a graphics-intensive game for 15 minutes.

If solid blocks of colours or pixel formations flash onscreen, you've pushed your GPU too far; restart the PC and roll back a few increments. Most contemporary PC components are sturdy enough to withstand this kind of tinkering, provided you roll back to a stable setting at the first sign of trouble.

Overclock your PC's RAM

It's possible to overclock your PC's memory, although you should use only matching modules (with the same speed, manufacturer and so on). Also note that it's easier (and safer) to install more memory than to overclock what you already have.

Launch CPU-Z and select the SPD tab to check your memory specifications. Then boot into the Bios and select either the Performance or Configuration menu, depending on your motherboard manufacturer. Enter the configuration menu for your memory and disable the default memory profile.

Adjust your memory multiplier by selecting a preset overclock option or by typing in the RAM clock speed. Use increments that match consumer-grade products (DDR3 RAM is sold in increments of 800, 1,066, 1,333, 1,600, 1,867 and 2,133). Save the changes and stress-test using MemTest.