This "broad strategic partnership" beween Nokia and Microsoft comes two days after Nokia chief executive Stephen Elop sent a bluntly worded memo  to his staff warning that the company was in dire straights, on a "burning platform".
The partnership is widely seen as a response to the problems outlined in the memo, in which Elop said that Nokia urgently needed a new strategy after falling "years behind" rival smartphone makers whilst simultaneously being threatened by Chinese manufacturers at the lower end of the market.
Monitoring firm IDC reports that Nokia's share of the smartphone market fell from 38 per cent to 28 per cent in 2010.
Under the new deal, Nokia will use the Windows phone operating company for its smartphones and Nokia's current smartphone operating systems will eventually be sidelined.
Although Nokia will continue to make phones using the current Symbian phone operating system, Symbian will become a "franchise platform".
Nokia Maps will become part of Microsoft's mapping services and Microsoft Bing will power Nokia's search services.
The Meego operating system, which was expected to become the core of Nokia's tablet and smartphone output, has been sidelined, although the company still plans to ship one Meego device by the end of the year.
How Nokia will juggle three different operating systems: Windows, Symbian and Meego, is one of many issues that Elop, a Canadian former Microsoft executive and the first non-Finn to lead Nokia, will have to address if he wants this brave move to be a success for the company.