Software giant Microsoft has launched Windows XP, the latest version of its main product, with a $250m marketing drive to push it to businesses and consumers.

It is being co-ordinated across 63 cities around the world. Microsoft chairman Bill Gates is hosting a launch in New York, while in London the company's chief executive Steve Ballmer presided over the launch party.

Microsoft claims XP is the biggest advance in its product range since the launch of Windows 95.

But critics said behind the software's pretty face is a technology core very similar to that many companies are already using.

Festival launch

With XP Microsoft finally leaves behind the decades old technology that contributed to the unreliability of previous versions of Windows.

Microsoft claims that because XP is built around the core of its Windows NT operating system it is far less prone to crashing.

Windows XP rolls off the production line

"It's the Windows to beat Windows," said Steve Ballmer at the UK launch held at the Royal Festival Hall on London's South Bank.

A number of stunts were scheduled in the UK to give XP a good send off.

The PC World store at Staples Corner in London was one of several computer stores that opened at midnight to sell copies of XP.

To show off the multimedia capabilities of XP a band called Electric Soft Parade are attempting to produce and broadcast the fastest ever music video using the movie maker program bundled into the operating system.

Sale maker

But despite the hype few expect the launch of XP to lift the technology industry out of its doldrums.

Global shipments of PCs tumbled by over 10% in the third quarter, its first decline since 1986, according to recent figures.

In an interview with BBC News Steve Ballmer acknowledged that the timing of the launch may be less than ideal.

"I understand that, certainly, in tough economic times it is not the best time to introduce any new piece of work," he said, though he insisted that the software was very "exciting".

Bill Gates will be in New York for the XP launch

Microsoft itself has trimmed its prediction for the quarter that ends in December and said it now expects PC sales to fall 2%, rather than stage a small recovery.

This could be because many businesses have already committed themselves to Windows 2000 and will not change their plans just because a slightly different alternative has become available.

There are concerns that consumers may prove reluctant to adopt XP, given that many will need to buy a new computer to use it.

Microsoft is also facing continued investigations over its alleged anti-trust activities from the EC.

In the US it faces legal action from InterTrust on technologies that sit at the heart of everything Microsoft wants to do with XP. And 18 US States are pursuing legal action against Microsoft.