Gates and Allen officially established Microsoft on April 4, 1975, with Gates as the CEO. The original name of "Micro-Soft" (short for microcomputer software) was suggested by Allen.

Microsoft moved its headquarters to Bellevue, Washington in January 1979.

Microsoft entered the operating system (OS) business in 1980 with its own version of Unix, called Xenix.

After negotiations with Digital Research failed, IBM awarded a contract to Microsoft in November 1980 to provide a version of the CP/M OS, which was set to be used in the upcoming IBM Personal Computer (IBM PC).

Paul Allen resigned from Microsoft in 1983 after developing Hodgkin's disease.

Microsoft released Microsoft Windows, a graphical extension for MS-DOS, on November 20.

Microsoft moved its headquarters from Bellevue to Redmond, Washington, on February 26, 1986.

On March 13, Microsoft went public (Public Company).

Microsoft released its version of OS/2 to original equipment manufacturers (OEMs) on April 2, 1987.

On May 22, Microsoft launched Windows 3.0, featuring streamlined user interface graphics and improved protected mode capability for the Intel 386 processor.

The company was at work on a 32-bit OS, Microsoft Windows NT. It shipped on July 21, 1993, with a new modular kernel and the Win32 application programming interface (API), making porting from 16-bit (MS-DOS-based) Windows easier.

Following Bill Gates' internal "Internet Tidal Wave memo" on May 26, 1995, Microsoft began to redefine its offerings and expand its product line into computer networking and the World Wide Web.

The company released Windows 95 on August 24, 1995, featuring pre-emptive multitasking, a completely new user interface with a novel start button, and 32-bit compatibility; similar to NT, it provided the Win32 API.

On January 13, 2000, Bill Gates handed over the CEO position to Steve Ballmer, an old college friend of Gates and employee of the company since 1980, while creating a new position for himself as Chief Software Architect.

On April 3, 2000, a judgment was handed down in the case of United States v. Microsoft Corp.

On October 25, 2001, Microsoft released Windows XP, unifying the mainstream and NT lines of OS under the NT codebase.

The company released the Xbox later that year, entering the video game console market dominated by Sony and Nintendo.

In November 2005, the Xbox 360 was released. There were two versions, a no-frills version for $299.99 and a bells-and-whistles version for $399.99.

The Total Assets of Microsoft corporation in 2006 was 69,597 mil. US$.

The Total Assets of Microsoft corporation in 2007 was 63,171 mil. US$.

The European Union imposed another fine of €899 million ($1.4 billion) for Microsoft's lack of compliance with the March 2004 judgment on February 27, 2008, saying that the company charged rivals unreasonable prices for key information about its workgroup and backoffice servers. Microsoft stated that it was in compliance and that "these fines are about the past issues that have been resolved".

Gates retired from his role as Chief Software Architect on June 27, 2008, a decision announced in June 2006, while retaining other positions related to the company in addition to being an advisor for the company on key projects.

Windows 7 was officially released to the public.

The Total Assets of Microsoft corporation in 2010 was 86,113 mil. US$.

Microsoft is a founding member of the Open Networking Foundation started on March 23, 2011.

On June 25, Microsoft paid US$1.2 billion to buy the social network Yammer.

On July 31, they launched the webmail service to compete with Gmail.

On September 4, 2012, Microsoft released Windows Server 2012.

Microsoft released Windows 8.

On March 29, 2013, Microsoft launched a Patent Tracker.

On September 3, 2013, Microsoft agreed to buy Nokia's mobile unit for $7 billion.

On February 4, 2014, Steve Ballmer stepped down as CEO of Microsoft and was succeeded by Satya Nadella, who previously led Microsoft's Cloud and Enterprise division.

On April 25, 2014, Microsoft acquired Nokia Devices and Services for $7.2 billion.

On September 15, 2014, Microsoft acquired the video game development company Mojang, best known for Minecraft, for $2.5 billion.

On January 21, 2015, Microsoft announced the release of their first Interactive whiteboard, Microsoft Surface Hub.

On July 29, 2015, Windows 10 was released.

On March 1, 2016, Microsoft announced the merger of its PC and Xbox divisions, with Phil Spencer announcing that Universal Windows Platform (UWP) apps would be the focus for Microsoft's gaming in the future.

On January 24, 2017, Microsoft showcased Intune for Education at the BETT 2017 education technology conference in London.

On October 10, 2018, Microsoft joined the Open Invention Network community despite holding more than 60,000 patents.

February 20, 2019 Microsoft Corp said it will offer its cyber security service AccountGuard to 12 new markets in Europe including Germany, France and Spain, to close security gaps and protect customers in political space from hacking.