"If it ain't broke, don't fix it" isn't a maxim that holds particularly true in the world of computer software. "If it ain't broke, spend hours trying to make it work even better" is nearer the mark. Promises of new features and trouble-free computing eventually persuade us to upgrade, leading to that same feeling of mild unease you get when someone tidies your desk: things we expect to find are no longer there, or have been replaced by things deemed to be a vast improvement.

This hasn't deterred Mac users, though. More than 2 million copies of Mac's new operating system, Leopard, were sold in the first weekend. I was one to make the knee-jerk purchase.

Many of the apparent changes are cosmetic. As "hiphopboy" commented on the Cyberclinic blog this week, "aside from nice email stationery and a couple of tweaks, it's hardly life changing stuff, is it?" Well, to call any software "life-changing" is leaving yourself open to ridicule, but Apple has built a back-up facility into Leopard, called Time Machine, which, to exaggerate further, is a potential life-saver. You can pick up a 500GB external hard disk for £75, plug it in, and the work is done for you. And you can go back an hour, a week, a month, and see a snapshot of your computer at that time. So you can either recall a single file or the entire disk.

Time Machine is deeply sophisticated. For us, it's just a couple of buttons. No tricky decisions to make, no trade-off between safety and drudgery. And as such, it will be indispensable. As is generally the case, my upgrade has required more than one attempt, and there are annoyances: my word processor's word-count facility no longer works, and I don't like the transparent menu bar. But Time Machine has already proved tremendously useful. Leopard might only seem like a sweet-shop full of eye candy – but an idiot-proof back-up system? That's nearly worth £85 on its own.

Diagnosis required

Contribute to next week's column by following the daily blog at www.independent.co.uk/cyberclinic. Topics coming up: Could graffiti replace passwords? And why is the internet community finding captioned photos of cats so fantastically amusing? Email any technology queries to cyberclinic@independent.co.uk