The number of PCs that are thrown away could hit 2.4 billion by 2013, says Nottingham University.

The 'Software marketing and e-waste: Standards for Sustainability' study by the university's Business School revealed that relentless pressure on consumers to upgrade their software is contributing to the increase in waste PCs.

Professor Peter Swann said many computers that are in perfectly good working order are rendered obsolete by up-to-date software versions that drain system resources in a process known as 'software bloat'. "The principal solution to the problem of PC e-waste is for developers and marketers to stop using strategies that contribute to bloat and enforced upgrading," said Swann.

Swann said the introduction of an industry standard that "discourages such a dysfunctional approach" would be applauded by both vendors and consumers.

According to Swann, Moore's Law - the theory that the power of a computer chip doubles every two years - has lead to software developers creating programs that use more processing power and memory than necessary.

Swann also blamed 'bundling' or selling PCs with huge amounts of pre-installed software that slows them down, and the need to download regular security upgrades, as key contributors to e-waste.

The study also highlighted that only half of all the PCs ever sold are still in use, proving consumers are struggling to find a productive way to use older machines.

"Passing off old tools to developing countries may look like charity, but it consigns the country to a perpetual lack of competitiveness," said Swann. "Even charities that recycle old computers to schools in the least developed countries have to set limits on what they can accept."