Hanover - When looking to buy a Mac, review the performance data for the individual models carefully. The differences between models are big, according to a recent study by the Hanover-based c't magazine. That applies to the optional features, the processing power, and the expandability options for the individual systems.

For general office applications, the Mac mini (around 500 dollars) is generally enough. Another introductory model in the Apple program is the MacBook, which is more expensive than other comparable laptops with identical performance. Users who want a MacBook anyway should wait for the next generation, the experts recommend. It may be released before the year is out.

Hamburg - If speed matters when transferring data, then consumers can hardly go wrong when buying an external hard drive. The Hamburg-based Computer Bild magazine recently tested eight devices in the 2.5 and 3.5 inch format, and the results were encouraging.

The devices all received a grade of "good" for their speed. The noise levels on the hard drives were also checked, with most models barely audible, the magazine reports. The test did reveal that many models run very warm, which can have a negative effect on service life, the experts feel.

Berlin - DVB-T - digital television received using an antenna - is available in a growing number of cities and countries. It's even possible to watch DVB-T on a laptop. The easiest way to do so is using a USB stick as a receiver.

"There are also cards for the PCMCIA slot on older laptops," says Michael Wolf, hardware expert from the German consumer testing organisation Stiftung Warentest in Berlin.

Paderborn, Germany - A ride on the oldest stretches of New York's subway is no further away than a quick trip to the video game store, thanks to World of Subways - a new simulator program.

Washington - The Windows Explorer file manager is one of the most frequently used applications in Windows. That's no surprise, really, since files, after all, are what computers are all about. And you need a file manager to see, copy, delete, and move them. You'd think, then, that this most basic of tools could be easily customised to work the way people want. And you'd be right - up to a point. The trouble is that Windows Explorer has more than its share of quirks - even bugs. Getting around them is what this week's answers are all about.

London, Oct 10 : Data security worries could soon be an anxiety of the past, courtesy the world''s first computer network protected by unbreakable quantum encryption.

The EU-sponsored project (called SECO-QC) has been successfully demonstrated at a scientific conference in Vienna.

The network connects six locations across Vienna and in the nearby town of St Poelten, using 200 km of standard commercial fibre optic cables.

The kinds of security schemes used on computer networks today are typically based on complex mathematical procedures, which are extremely hard for outsiders to crack, but not impossible given sufficient computing resources or time.