Microsoft has joined forces with the developers of the "$100 laptop" to make Windows available on the machines.

The move was prompted by countries which demanded the operating system before placing an order.

Trials of laptops loaded with Windows will begin in "four to five" countries from June, the organisations said.

The founder of One Laptop Per Child (OLPC), which developed the machines, denied the move was a "desperate new measure" to secure more orders. "While it is certainly true that it has not taken off as fast as I would have hoped and publicly stated, certain countries around the world... have always been very, very insistent that they want Windows as an option," Nicholas Negroponte told BBC News.

Until now, the XO machines, as they are known, have only been offered with an open-source Linux operating system