Microsoft started as Traf-O-Data in 1970 as a traffic computer manufacturer for traffic lights for the Washington roads, the company was working for the government at the time and later moved to Microsoft on April 4, 1975.
Microsoft launched its most well-known logo in early 1987, and since then, has been cherished by many. It's still used on older products and some portals (most notably the Windows/Microsoft Update website and Boot Screen in Windows XP, the Microsoft Update site in Windows Vista, and the documentation page for Windows XP Professional, and some others, just to name a few). It was designed by Scott Baker.
“The new logo, in Helvetica italic typeface, has a slash between the o and s to emphasize the "soft" part of the name and convey motion and speed.”
—Scott Baker, designer of the 1987 Microsoft logo.
With the launch of a new slogan in 2011, the Microsoft logo was altered slightly, reducing the slant.. This logo was the shortest-lived ever, only being used for one year until August 22, 2012.
Microsoft launched its new logo on August 23, 2012, which includes four squares with the colors of the then-current Windows logo. Although this logo cannot be completely current, a similar one was featured in Windows 95 commercials from the mid-90's.