Despite a high profile, multi-billion dollar advertising campaign and protestations that Vista is doing well, Microsoft has given Windows XP yet another official reprieve.

The software giant has extended the deadline for PC markers to buy licences for the old operating system, meaning XP will still be on shop shelves months after it was supposed to disappear in favour of Vista.

The cut off date was the end of January 2009, but licences from Microsoft will now be able to be obtained until 30 May 2009.

Microsoft has already extended the deadline for the use of XP in netbooks until 2010, but this major move is being described as a "yet another sign of the market's resistance to Windows Vista" with both business - and consumers - said to be willing to skip Vista for Windows 7.

The latest industry rumblings suggest Windows 7 could launch as early as Christmas 2009.