Those companies have yet to announce if they will also patch Windows 7 after 2020.

Nicole Peng, research director at industry consultancy Canalys China, said most businesses in China still use Windows 7.

But piracy issues and the Chinese government's security concerns connected with the use of overseas software have made it difficult for Microsoft.

Regulators banned Windows 8 in government procurement deals in 2014 and are investigating if the company's Office software and Windows systems have violated the antitrust laws.

Charlie Dai, principal consulting analyst at Forrester Research, said although the investigation could set back Microsoft's China business, local vendors will still find it difficult to edge into the market because software products from the US company are already tightly integrated into many business applications.