Windows 4.0 – August 24, 1995 - Windows 95, 98, 98 Second Edition, and Millennium
All of these versions started an underlying layer of MS-DOS before Windows itself could load.
Windows 95 used a special mode of the 80386 processors called “Enhanced Mode." This brought (theoretical) two-gigabyte memory addressing and virtual memory, which was the ability to use parts of memory that were non-contiguous (i.e., scattered around in the memory map).
Windows 98 added USB support and integrated Internet Explorer into the OS. This was a decision that had long-reaching repercussions. United States vs. Microsoft was the first of the lawsuits.
Windows 98 SE brought Internet Connection Sharing, fixed some stability problems, and was probably the most stable version of Windows to date.
Windows Millennium Edition introduced System Restore, improved Internet, and multimedia features. Windows ME was as unstable as 98 SE was stable, and it earned the moniker “Windows Mistake Edition." PC World put Windows ME fourth in their list of the twenty-five worst tech products of all time.
Windows ME was also the last version of Windows to be based on MS-DOS
Next: Windows 5 (Windows 2000 and Windows XP), Windows 6 (Vista), Internal/External Numbering, and Further Reading