At the glitzy launch of its last Windows operating system, Vista, Microsoft promised that "the wow starts now" - but when the "wow" turned to "ugh", the company found itself regretting the big promises.

So, when the software giant launches Vista's successor, Windows 7, today, it is expected to take a decidedly lower-key approach, emphasising the increased speed and efficiency of the new operating system.

In Paris, the company has opened a pavement cafe to show off the product. In New York, the chief executive, Steve Ballmer, will haul onstage the four-year-old girl who is the face of the Windows 7 ad campaign.

But the events are a far cry from the days in the last decade when consumers would queue round the block to get their hands on an upgraded version of Windows.

Vista underperformed because many businesses refused to upgrade from Windows XP, citing numerous technical glitches, but Microsoft believes that Windows 7 will restore the company to revenue growth after a 17 per cent decline in the last quarter.

Stephen Schuckenbrock, spokesman for the computer maker Dell, said he expected strong business demand for PCs from the middle of next year.

"When you consider that Vista was a bust, Windows 7 is a capability upgrade on a scale that has really never been seen before."