Nicholas Turnbull's special diagram proved so successful that in just 79 minutes it had been sent to computer users on all five continents of the world, including a base on Antarctica and an office in the US's top-secret defence building, the Pentagon.

Computer whizz Nicholas (19), a former pupil at Bishop Luffa and now studying computing with artificial intelligence at the University of Sussex, designed the special flowchart for friends and family to help them work out which files were unsafe.

He thought of the idea just two weeks ago and already it has helped millions of people across the world avoid corrupt files.

"I was tired of people asking me to help them when viruses appeared on their computer so I dreamed up this simple flowchart which anyone can follow," explained Nicholas, of Ormonde Avenue, Chichester.

"I've distributed it free so nobody has to pay to deal with this often-expensive nuisance.

"I wanted to apply my cognitive science theories on information in some sort of experiment.

"The poster uses the minimum of verbal explanation, instead using schematic arrows and colour to show what parts refer to which.

"I think this sort of format could prove useful for communicating technical information without assuming prior understanding of technical terms."

And Nicholas believes the chart is the best way for all computer users to protect themselves.

"I personally think this chart might be a more effective security tool than anti-virus and anti-spyware software combined," he said.