We might live in an increasingly cynical world but most of us still like to help out others when we can. So if you were offered a way to help the thousands of families affected by illnesses every year, we doubt you'd turn away.

Distributed computing, usually referred to as a 'grid', puts your home computer to work for a good cause and you don't have to lift a finger or pay a single penny. Grid computing takes advantage of your computer's idle time, which occurs more often than you might think.

Even when running applications, only a small amount of its true potential is used. It may sound strange, but the full power of a computer is rarely needed. To get a visual idea of this, fire up your Task Manager by holding down the Control and Alt keys, then press the delete key. Click on the Performance tab and see how often your CPU Usage, or processor, hits 100 per cent.

Millions of computer users are lending their PCs' processing power to medical and scientific projects around the world. As well as fighting illness, you can help scientists discover the secrets of the big bang or if there is life beyond our planet, or help create the world's largest chess brain.

The grid revolution
Anyone can join the grid computing revolution. It won't slow down your computer, it doesn't cost you anything and you don't need specialist knowledge of the technical details of the project your computer is working on.

So how exactly does it work? The projects have to analyse a huge amount of information in order to deduce any conclusions. Instead of building supercomputers to crunch all this data, grid-computing projects break up the problem into bite-sized chunks. These are sent to volunteers' computers to be worked on. Once your computer has solved its own small task, the results are sent back to the main project computer for collation.

It might not sound like much, but the cumulative effect makes a serious impact on the time it takes scientists to break down complex problems, such as studying gene chains in DNA.

To get started, decide which project you want to help (see Choose your project below) and then visit its website to download and install a small application. These programs vary in size. Oxford University's, which is used to help find a cure for cancer, is only 1.5Mb. That means a four or five minute download on a standard dial-up internet connection.

The program that helps search for extraterrestrial life comes in at half that size. Once fired up, your PC will automatically connect to the project when you are online to send and receive data. The only indication that your PC is working on your chosen project is a special screen saver. If you don't like the screen saver, you can turn it off by right-clicking on the Desktop, then selecting Properties and clicking on the Screensaver tab.

The grid applications are smart and polite. There are few PC tasks that will be affected by the grid software, but if you want to do some work that really puts your processor through its paces, such as video or image editing, the grid program will step aside and close itself down to let you finish.

When sufficient processing power becomes available, it will start up again. A small icon will become visible in your System Tray, and if you want to change any settings, such as when or how often the grid application uses your internet connection, you can click here to make changes.

Making a difference
The most famous project currently under way is the Search for Extraterrestrial Intelligence, or SETI@home for short. The project, created by the University of California, has been using home computers to analyse data captured by radio telescopes for signs of artificial signals. In other words, real evidence that ET is trying to get in touch.

It has been running since 1996 and within five years had accumulated half a million years worth of processing time, with the help of half a million users. "Why let your home computer waste millions of CPU cycles running a screen saver when it could be analysing SETI data?" the project asks. "Computer users from around the world are able to participate in this major scientific experiment."

The Oxford University cancer project is a bit closer to home and, to many, a more realistic and worthy project. It describes itself as the "world's largest ever computational project", and is analysing 3.5 billion molecules to work out their cancer-fighting potential.

Oxford University is convinced of the value of grid computing. "It allows research of amazing scope and complexity. If this project is successful, the public contribution of computing power could become one of the most powerful tools available to modern drug research," says its website.

Professor Graham Richards is the chairman of chemistry at Oxford University, and he is quick to point out the benefits of grid computing. "We have nearly 2.9 million PCs signed up," he said. "This has provided 360,000 years of CPU time, and built a virtual computer that has more power than the world's biggest supercomputer. We can screen billions of drug-like compounds in weeks. So far we have looked at 14 cancer targets, anthrax and smallpox."

The processing power at the university's disposal is roughly equivalent to working out a difficult equation a hundred-trillion times a second. It is enough to make the mind boggle.

Bringing us back to the real world, Professor Richards is confident that the project will make a real difference to real people. "It ought to knock a couple of years off the discovery stage of a drug discovery process," he said.

As well as helping with hugely complex research, donating processor time has another benefit: you become part of a community and can keep track of the achievements you and your PC have made. You and your friends can create a team or join existing teams, so you can support each other's search for a cure.

Members of the grid are told when they find 'hits', molecules that have been targeted for further research. There are also chat rooms for members to compare notes. "Participants do feel personally involved and learn much about the actual process," said Professor Richards.

CHOOSE YOUR PROJECT

Cure Cancer
www.chem.ox.ac.uk/curecancer
A project carried out by Oxford University's Centre for Computational Drug Discovery, and funded by the National Foundation For Cancer Research. It uses very little processing power, and requires a computer with just a minimum specification of 48Mb of memory, a 500Mb hard disk, with at least 20Mb spare.

When you join you become part of a family of users, and can join groups and contribute to the chat rooms. Sadly those with Windows 95 or Apple Mac computers cannot run the software.

There is already a Computeractive team up and running on this project and, thanks to our readers, the team has clocked up almost 120 years of processing time for the project. To join us, download the software and go to www.grid.org, type 'Computeractive' into the search window and press enter. Or set up your own team and see how you do against us.

SETI@home
setiathome.ssl.berkeley.edu
This project analyses radio telescope data looking for unusual readings which could be signs of aliens trying to communicate with Earth. In August this year, New Scientist reported that one particular signal was extremely promising, and could in fact be a sign of extraterrestrial life. While the story was played down by SETI@home's chief scientist, Dan Werthimer, it was not ruled out.

A similar low-spec computer is needed as for the last project, but SETI uses more processing power and so is used only when your PC is not in use and switches to screen saver mode.

Climate Prediction
www.climateprediction.net
One of the more recent grid computing projects, Climate Prediction, uses computing power to try and forecast climate in the 21st century. It describes climate change as an issue of global importance, which affects everything from food production to insurance costs. It is hoping to predict what will happen to our world after the impact of global warming really begins to bite.

There are just 20,000 participants taking part in the project, which explains why the project recently joined the network that looks after the SETI project. Prior to that it was carried out by the Open University, the National Environment Research Council and the Department for Trade & Industry.

Lifemapper
www.lifemapper.org
This project aims to build a detailed picture of life on Earth, so that scientists and environmentalists can start the mammoth task of predicting the impact of global climate change.

Run by the University of Kansas, the researchers behind it hope the results will also be of use to conservationists, who can use the data to educate governments and public alike about Earth's biodiversity and our effect upon it.

The Distributed Hardware Evolution Project
www.informatics.sussex.ac.uk
Ever wished that your computer could detect when it was malfunctioning and then fix itself? That golden scenario may be a long way off, but scientists at the University of Sussex are working to develop electronic circuits that can diagnose their own problems.

The potential value of the work is enormous, as technology increasingly manages what are called critical systems, such as those inside aircraft, medical equipment and power stations.

The project gives your computer the chance to host a virtual island, where various types of theoretical circuits fight for survival. Those that figure out how to survive are sent back to the project for detailed analysis.

Safety at work
One of the first things that computer users say when hearing of projects that access their computer is that it doesn't sound very secure. While, as ever, security must be taken seriously, you will find that grid computing is relatively safe.

SETI answers users' concerns by claiming that the screen saver is much safer than the browser being used to ask the question! It is a compelling point. Your firewall will block the grid project at its first attempt, but that's because all programs that are trying to access the internet for the first time from your PC are challenged.

As for privacy, your files or personal folders cannot be accessed by lending processing power to these projects, and neither will you become vulnerable to viruses because none of the data comes in a format that viruses take in order to work.

All of the projects we have looked at in this piece have comprehensive lists of frequently asked questions about their purpose which will answer any query you might have on potential security or privacy worries.