Gates was forced to rebuild Windows Vista

Microsoft was forced to scrap the first incarnation of Longhorn – now called Windows Vista – after a senior executive warned chairman Bill Gates that it was too complex to work properly.

Jim Allchin, group VP in charge of Windows, told the Wall Street Journal he dropped the bombshell last summer, simply telling Gates "It's not going to work". Longhorn was so complex that Microsoft's developers would never be able to make it run properly, Allchin told Gates.

The root of the problem was Microsoft's historical approach to developing software – the so-called 'spaghetti code culture' – where the company's thousands of programmers would each develop their own piece of code and it would then all be stitched together at the end.

According to the WSJ interview, Allchin faced opposition to his call for a completely new approach to how Microsoft develops Windows – firstly from Gates himself and then the company's engineers.

The new approach was to develop a clean solid core code base for Windows which new features could more easily be added to over time and Allchin introduced new tools that would automatically reject buggy code.

As a result of this Microsoft received thousands fewer bug reports than usual when it released the beta version of Windows Vista this summer. Allchin's culture change also appears to be spreading through the rest of Microsoft. Gates said the new tools are now being used by the Office group. "I wish we'd done it earlier," he told the paper.