The investigation into the kidnapping of Natascha Kampusch has been complicated by the discovery of an obsolete computer in the house where she was held, Austrian police said today.

Officers have been surprised to find that the kidnapper, Wolfgang Priklopil, a communications technician, appeared to have relied exclusively on a Commodore 64.

The beige-coloured machine was popular in the 1980s but is now considered an antique, though some electronic dance acts still use it and it has a cult following among some fans of retro computers.

It was hoped that the computer might contain information which might shed more light on the decision of Priklopil, 44, to snatch Ms Kampusch, when she was aged 10, in March 1998.

However, Major General Gerhard Lang of the Federal Criminal Investigations Bureau, told reporters the computer would complicate investigators' efforts to transfer files for closer examination.

There are emulators available which can make a modern PC capable of running Commodore 64 programmes but Maj Gen Lang said it would be difficult to transmit the data from Priklopil's machine to a modern computer "without loss".

Priklopil killed himself by jumping in front of a train within hours of the escape of Ms Kampusch, now aged 18, on August 23 this year. He had mostly kept her in a tiny, secret, windowless room under his garage at his house, in suburban Strasshof, just north-east of Vienna.

Police have been digging pits and using long probes to poke around the property, to ensure the house and garden do not conceal any other secret underground cells.

So far, none have been found, Maj Gen Lang said, adding that there were no plans to question Ms Kampusch about her ordeal any further.

Austrians have been captivated by the story, not least because Ms Kampusch has said she mourned the man who captured her, and some experts believe she is displaying signs of Stockholm syndrome, in which captives identify with captors.

A huge audience is expected to watch Ms Kampusch's first television interview, which was being recorded today and will be broadcast tomorrow evening by public broadcaster ORF.

So far, the Austrian public, hungry for details, has been shown only photos taken before her kidnapping in 1998, or computer-generated likenesses of what she might look like now.

However, people hoping for a glimpse of Ms Kampusch might be disappointed: organisers said she would appear behind a screen in silhouette or, at most, in camera angles taken from behind or over her shoulder to respect her privacy.

ORF also said it would not ask Ms Kampusch anything "intimate," steering clear of questions about whether her captor sexually abused her.

Ms Kampusch has been besieged by hundreds of requests for interviews since she escaped two weeks ago, but so far she has agreed to grant only three: the one to ORF, another to the mass-circulation daily Kronen Zeitung, and a third to the weekly magazine News.

Ms Kampusch has a media adviser, Dieter Ecker, who said: "For Natascha Kampusch, it was natural that the Austrian people - who have feared for her life for eight years and have celebrated her escape - should get the details first." Christoph Feurstein, the ORF journalist conducting the interview, said: "It's entirely up to her to decide whether to show her face." The station said it did not pay for the interview but announced today that it had set up a telephone hotline for Austrians to pledge cash donations to Ms Kampusch.