The Russian competition regulator has dropped an investigation into Microsoft's decision to stop sales of XP in favour of Windows Vista.

The Federal Antimonopoly Service began the probe in June. It accused Microsoft of stopping XP sales to to retailers and OEMs (Original Equipment Makers), even though there was continued demand for the older operating system. The regulator also investigated why OEMs and retailers were charged different prices for the same operating systems.

Microsoft is obviously keen to move customers on to its newest operating systems not just to increase licensing payments but also to reduce support costs.

It faced a tough task persuading users, and corporate IT departments, that the move from XP to Vista was worth it.

Russian customers can still get their hands on XP and Microsoft Russia told Reuters that they would start an exchange programme to switch copies of Windows Vista for XP until the end of 2009.

The FAS is continuing a separate investigation into Microsoft's dealings with laptop makers in Russia. ®