A new market for used PCs is thriving because people want to get licensed copies of Windows XP, according to industry analysts and hardware suppliers.

Research firm Gartner said lots of PCs have been disposed of because Microsoft's Windows Vista OS has created a demand for PCs with greater hardware capabilities. In 2007, about 197 million PCs were discarded, of which 44 percent were put up for sale second hand. Traditionally, used PCs have been repurposed by those seeking cheaper PC components, but Windows XP's continued popularity means people are now looking for alternative ways to legally get hold of the operating system (OS).

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Windows XP licence IDC research manager David Daoud said old copies of Windows XP remain popular because home users and businesses need the older OS to run legacy software.

"The other main reason we see people staying with XP is for standardisation. Having five PCs that are Vista and five XP can create training issues and compatibility issues [for businesses]," added Josh Kaplan, president of Rescuecom, a computer repair firm in the US which resells XP-based computers to businesses.

However, Kaplan warned Windows XP fans to be careful where they buy licences for the OS. He said buyers should be careful when buying PCs from eBay, as many systems sold on the online auction site contain illegal versions of XP.

With additional reporting from Agam Shah