History: 1995 was a nice year for Windows, when the company launched Windows 95. Then came Windows 98. So far, so good. 
Then something happened. Microsoft took a mis-step. Windows “Millenium” came out. It was a hybrid between the uber-stable Windows 2000 and Windows 98. Since it was neither here nor there, it flopped.
XP was and is a great operating system from the frame of mind that it cemented Windows as the operating system of choise for desktops. Then Microsoft did something. It promised and it delayed XP's successor: Vista.
Vista is comparably the Millenium operating system of today. Instead of belabouring why Vista failed, it is my belief that Microsoft has finally gotten it right with Windows 7.
Why?
Three reasons. First, Microsoft learnt from its expensive mistakes with Vista. Second and more importantly, Microsoft took an open-source community approach with 7's release. Third, 7 was built with a modular architecture in mind. All previous Windows were like elephants, designed like it was “all or none.”
What will make Windows 7 a Successful?
1) Software and hardware drivers work
2) Reasonable price as compared to the price of XP
3) Read here…
Will 7 be the operating system that will make MAC notebooks a less compelling offering than PC notebooks? I think so.
Windows 7 is scheduled to be released in January 2010, but the market is anticipating that it may be released later this year. When Vista's release date was announced, MS ended up delaying it…and delaying it again, so it would appear that PR is managing expectations to the level that it might surprise disgruntled Vista and overly-satisfied XP users.
Disclosure: Long on Microsoft shares here.