Microsoft Windows 3.1 Bill Gates & Microsoft had witnessed the revolution of the Macintosh, and knew that the only way they could maintain their hold over the PC OS market was the creation of a layer over MSDOS called Windows. It took 3 versions and several years until Microsoft developed an operating system that could compete against Apple. Internet Explorer, Microsoft Office, NT and other initiatives fueled this OS, one that would lead the PC industry through the next 20 years.
	Macintosh System / MacOS After the enormous success of the Apple II, and the utter failure of the Lisa, Apple followed up with the Macintosh. The Macintosh desktop icons were based heavily on the Lisa, but were more streamlined and held a 32 x 32 pixel footprint that became commonplace in the PC industry for years (Again, heavily based on the Xerox Star). The monochrome icons were designed by Susan Kare (who later went on to design the icons for Windows 3.0). The document icons were similar to those from the Xerox, while applications relied heavily on the diamond shape. These icons were the building blocks of each Macintosh system software that followed, but were ultimately userped by the new style of Mac OS X icons.
	Xerox Star Xerox developed the modern WYSIWYG interface far earlier than the Macintosh's insanley great UI. The Xerox star held modern looking 72 x 72 icons and developed many of the standards that appear today, from document appearances to icons that change in appearance. The Xerox star graphical user interface and corrresponding icons heavily influenced the way each subsequent user interace has appeared today.
	IBM OS/2 A combined effor by IBM and Microsoft to create an OS that proved to be a difficult relationship. Microsoft went to on to create Windows and IBM followed through to create a solid OS.