Microsoft's chief executive Satya Nadella said Windows 10 marks a "new era" for personal computing as the software was launched globally on Wednesday.

Windows 10 is offered as a free upgrade to existing Windows users and to those who are buying new PCs. Depending on the hardware, installation should take 20 to 90 minutes.

Satya Nadella told BBC that, "Windows 10 is a huge milestone for us as a company, and quite frankly the industry."

Final Launch - Windows 10

Every few years, Microsoft has launched an updated version of Windows. The company said that Windows 10 will be the last of this kind. And Microsoft is planning to update this every few months for free.

Nadella is more excited about Cortana and according to him Cortana is as important as the PC operating system.

According to analysts, Windows 10 was much awaited by the world. But the question here is, should it be upgraded for free immediately? Or will it be another Windows 8 moment?

-Sumana