Microsoft chief executive Satya Nadella introduces Windows 10 at a press event in Redmond, Washington on Jan 21, 2015. [Photo/ CFP]

Microsoft Corp is making its biggest push into the Chinese consumer computing market this summer by offering free upgrades to Windows 10 to all Windows users, regardless of whether they are running genuine copies of the software.

The move is an unprecedented attempt by Microsoft to get legitimate versions of its software onto machines of the hundreds of millions of Windows users in China.

Terry Myerson, who runs Microsoft's operating systems unit, announced the plan at the WinHEC technology conference in Shenzhen, South China's Guangdong province.

"We are upgrading all qualified PCs, genuine and non-genuine, to Windows 10," he said in a telephone interview with Reuters. The plan is to "re-engage" with the hundreds of millions of users of Windows in China, he said, without elaboration.

Myerson said Windows 10 would be released globally sometime "this summer". That is the first time Microsoft has put a time frame on the release, although it has been expected in autumn, based on Microsoft's release history.

Microsoft said in January it would offer free upgrades to Windows 10 for users of Windows 7 or later in an attempt to hold onto users and make up for lost revenue by selling services such as Office over the Internet.

Microsoft is working with Lenovo Group Ltd, the world's biggest PC maker, to help roll out Windows 10 in China to current Windows users, Myerson said.

It also is offering Windows 10 through security company Qihoo 360 Technology Co and Tencent Holdings Ltd, China's biggest social networking company, which will build a Windows 10 app that will work on smartphones and PCs for its popular QQ gaming and messaging service. QQ has more than 800 million users.

Lenovo said in a statement that it will make phones running Windows software, available through China Mobile, sometime later this year.

Microsoft also said it is working with Chinese handset maker Xiaomi Technology Co Ltd - which generally uses a form of Google Inc's Android on its devices - to offer some customers a test version of Windows 10 on their smartphones.