Apple's upgraded Leopard operating system was set loose on Friday as trend-setting iPods and iPhones cause the ranks of Macintosh computer lovers to swell.

Eagerly-awaited by Apple's notoriously cultish followers, Leopard's release was delayed so the company's engineers could devote their time to getting iPhones to market in the United States in June.

Leopard features include playful 'iChat' video-conferencing and a 'Time Machine that resurrects lost data. Time Machine was inspired by a survey that indicated only 26 per cent of Macintosh users regularly backed up information on their machines to avoid losing it forever in system crashes.

The feature automatically copies music, pictures, applications, files and 'absolutely everything' a person puts on their Macintosh, according to Apple vice president of platform experience Scott Forstall. The operating system enables people to remotely search for files on all computers connected to their network.

Leopard also has simple tools for people to create "widget" applications that stream feeds such as news or syndicated cartoons from websites onto small windows on computer screens. It includes improved text-reading, Braille support, and closed-captioning for people with disabilities.

Modifications to iChat allow people linked via web cameras to share slide show presentations, playfully distort their pictures or insert fake backdrops.

Rival Microsoft, whose software powers 90 per cent of the world's computers, released its own new operating system, Vista, in January.

Apple has been leveraging the popularity of its market-dominating iPod MP3-players and innovative iPhones to build on it's following of Macintosh users, according to industry analysts.