The Russian Federal Antimonopoly Service (FAS) has dropped its investigation into Microsoft’s decision to stop selling Windows XP in favor of Windows Vista. Russian customers can continue to buy XP, and Microsoft has said that it will kick off an exchange program soon to allow users to downgrade Vista PCs to XP up until the end of 2009. The FAS began a probe in July into why Microsoft was halting sales of the aging OS to OEMs despite there still being a demand for it. Questions were also raised into why OEMs and retail outlets were charged different prices for the OS. The FAS is still investigating some of the largest OEMs for violating antimonopoly legislation by pre-installing Windows on notebooks, reports.