Anyone who underestimated the power of Microsoft should learn a salutary lesson from the current gyrations in the US Nasdaq index. The technology-heavy market has suffered a series of precipitous collapses since the formal ruling of uncompetitive behaviour against the company in the court of Judge Thomas Penfield Jackson, even if it has recovered some of the ground subsequently.

No one is denying that the technology sector was suffering from investor nerves before the Microsoft news. After all, the index had gained more than a quarter of its entire value in the few weeks between mid-January and early March and a correction had been expected. Indeed, several blips had been seen as the start of just such a move, only for the index to rise again.

Still there had been nothing of the order of the 10 per cent-plus intra-day plunge of last week or the one-day fall of more than 7 per cent on Wednesday on the back of a 5 per cent fall on Monday and followed by the loss of a further 2.5 per cent on Thursday. It took Microsoft's woes to knock the stuffing out of the index to that extent.

Ironically, the behaviour of the index is probably as strong a confirmation of the accuracy of Judge Jackson's verdict as any that could be expected.