With Internet Explorer 9 on the horizon, it might be a good idea to have a look at all the present & earlier versions of Internet Explorer beginning from v 4 along with the Operating System version or products, each was associated with, purely for academic purposes!

The released versions of Internet Explorer for Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition (Me), Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003, and Windows Vista use the following format:

major version.minor version.build number.sub-build number

 This table includes possible Internet Explorer version numbers.

Sourced from KB969393.

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