Microsoft Corp on Thursday failed to quash fears that a new version of its Windows software system would be further delayed, stirring concerns that a new technology cycle tied to the upgrade could be put on hold.

This uncertainty over when Microsoft and the rest of hi-tech would benefit from the surge in revenue growth that typically accompanies a major Windows upgrade led Microsoft’s shares to close down 2 percent at $23.87 on the Nasdaq on Thursday.

We will ship Windows Vista when it is available Kevin Johnson, co-president of Microsoft’s platforms and services unit, said at the company’s annual financial analysts’ meeting, adding that Microsoft would take the project “milestone by milestone”.

Windows sits on more than 90 percent of the world’s personal computers.

Windows Vista, already five years in the making, has been postponed by Microsoft several times. Quality assurance delays have put off the consumer version of Windows until early 2007 — after the crucial holiday shopping season.