In a huge hall at the capital's largest exposition ground, the Pragati Maidan, Microsoft India chairman Bhaskar Pramanik and Windows director Vineet Durani opened Windows 10 to the Indian market, with which the Redmond, Washington-based company intends to compete with well-entrenched rivals like Google and Apple.

"Starting today, people who reserved their upgrade to Windows 10 will be notified in waves when their upgrade is ready to be installed," the company said at the high-profile launch event.

"For business customers, Windows 10 is available to start deploying within their work environments, and starting Aug 1, organizations that have volume licensing can upgrade to Windows 10 Enterprise and Windows 10 Education," the company added.

Windows 10, which will be available for a free upgrade for one year for users using Windows 7 version or higher, would have to be otherwise bought at a price of $199 for Windows 10 Pro and at a lower $119 tag for Windows 10 Home edition. Users who do not upgrade by one year will have to buy the new operating system.

More specifically, customers using older versions of Microsoft operating systems will first have to first upgrade to 8.1 to get the free update. Those not eligible will be required to pay for the new product.

"In India, more than 1,500 retail stores across the country will help consumers move to Windows 10. Also, many Indian and multinational partners are ready to offer a variety of Windows 10 devices," said Pramanik, after a brief introduction of the new offering.

Indian-born Microsoft chief executive Satya Nadella has targeted 1 billion users in the next three years. He was himself in Kenya interacting with the fan club of Windows operating systems, called "Windows Insiders" who also help in fine-tuning products.

Windows 10 comes with a redesigned web browser called Edge and Cortana, an Apple's Siri-like voice activated assistant, an Xbox gaming console app. The system covers a wide range of devices, including PCs, tablets, phones, Raspberry Pi, Xbox One, HoloLens and more -- with more than 2,000 devices or configurations already in testing, the company said."We are entering a new era of Windows. For the first time, we built Windows 10 alongside our customers -- the feedback of more than five million 'Windows Insiders' helped shape Windows 10," said Durani.