Microsoft celebrated its 30th anniversary at the company’s annual meeting on September 23, 2005. Here are few links that will give you lots of information on Milestones of Microsoft

The PC Timeline at PC Museum says "April 1975 Bill Gates and Paul Allen found Micro-Soft. The hyphen is later dropped to Microsoft."

Larry Osterman, on his 20 years with Microsoft worth reading

The History of Computing Project has a very detailed history of Microsoft from 1975 to 1998

The Histories of Microsoft according to encyclopedia Wikipedia, and Encarta

Official History from Microsoft available for download here

More FAQ’s on Microsoft History available at Microsoft.com Corp FAQ’s

Here is an interview with Marc McDonald, Microsoft's first employee and talks about the early days of working at Microsoft as well as what he's doing on the Windows Vista team (he's working on defect prevention). Download the video here

The Microsoft Visitor Center Timeline documents some of the most critical turning points along our 30-year journey. The Microsoft Timeline charts 30 years of software history
Follow a software giant from startup to success. Pinpoint the decisions and events that made all the difference.

A funny stuff here on Steve Ballmer selling Windows 1.0

What does the future hold for the computer software giant? BBC News

More News for you:
From the Microsoft press release

Here is an Interview of Bill Gates and Steve Ballmer by the Seattle Times. Get the audio recording (28mb) of the interview here

Here’s another interview by Seattle Post Intelligencer. And here are the audio files