Do you think Windows OS is being overthrown by its contenders?

I agree with all answers

Windows Operating Systems still have monopoly in the Market due to its very good compatiability with other systems and also it is always readily available.Every new version of windows O.S Comes with New Enhancements and features that makes it more competative and Lively against other Operating Systems.Secondly window Professionals are more then other o/s professionals.The type of methdologies and strategies Involved in Marketing  a Windows Product made it to be Always at ForeFront  then compared to other O/S competitors.For Many organizations still Windows is the Only Way for Operating their Systems !

NO WINDOWS STILL LEADING WHY BECAUSE WINDOWS STILL THE FRIENDLY USER OS COMPARE TO ALL CONTENDER.
ITS MEANS THAT WINDOWS OS IS THE EASIEST AND FASTEST OS YOU CAN LEARN EVEN WITHOUT FORMAL EDUCATION IN COMPUTER YOU CAN STILL LEARN COMPUTER IF YOU USE WINDOWS OS.

Yes the latest addition os8.1 has some glitches. It is advisable to wait and watch .Some drivers and .dll files may be missing. if your computer is having problem after upgrading it is advisable to downgrade to win8.

  Windows is being overthrown by its Contenders? I dont think so, beacsue Now in windows the stability of operating system is going very powerfull starting from Win7,Win8 , but for ubuntu it would still take much time to cover the market of Windows because still most of IT Persons dont like and prefer it because of the unease in its use as compared to windows OS for personal use.

As much people around the world use computers, as much as they stay away from using Windows operating systems.
Fisrt, I don't agree that widows was the first os was there, actually Mac systems was the first and Microsoft (tried to follow) and through buying the Xerox employee invention (the mouse) from there there was the famousness of Microsoft and windows os after.
Windows was not an os realy since its begining because it is based actually on DOS os, until the first real os (Vista) which face lots of problem solved on windows7 which didn't leave enough time for the vista to be tested according to its failure.
So, we have to conseder now the Android os which is based on Linux which is the giant of yesterday and tomorrow because of its GPL and the amount of coders working on fixing any failure or bugs.

I do not think...he was the first system to be established on the basisof multipleusers, and easy-to-use graphical interface...also is an operating system fits all