The gap between the 2001 release of Windows XP and that of Windows Vista in 2007, created a window of opportunity for the growth of rival operating systems from Apple and the open source community. However, despite the fact that both Mac OS X and Linux have increased their respective market share, neither proved capable of dislodging a consistent user install base slice from under Windows. When Windows Vista hit the shelves in January, the operating system was prophesied to drive users away from Windows and onto Linux and Mac OS X.

But while on the server side Linux indeed experienced a consistent increase in market share, outperforming even Windows Server, the same was not valid when it came down to client platforms. Linux timidly gained market share, but the open source operating system remains positioned at the periphery of the market. Of course, with the increasing adoption of Linux distributions by global original equipment manufacturers, and the pre-loading of the open source operating system on computers offered alongside Windows-based machines, the current status quo of undisputed underdog has the potential to evolve.

Apple is already making headways in this aspect, at least on the U.S. market. Pushed by the Cupertino-based company's proprietary hardware, Mac OS X 10.4 Tiger jumped to a market share of 6.61% at the end of September 2007, in comparison to Google's 0.81%. But Apple still has to release its response to Windows Vista. In fact, Mac OS X 10.5 leopard, the successor of Tiger is now in the final stages of the development process.

Apple postponed Leopard from mid 2007 to October in order to ship the iPhone on time. Now, Mac OS X 10.5 is close to finalization, according to AppleInsider. Apple has even debuted the training of its support staff in accordance with materials related to the new operating system. And the company reconfirmed at the end of the past month that Leopard was still planned for October. On September, Apple dropped Mac OS X 10.5 Leopard build 9A559, a move considered synonymous with the delivery of the release candidate of the operating system. Still, while Apple might very well be on the brink of declaring a build of Leopard Gold Master, it has failed to do so until this time.

When Leopard will hit the market, Windows Vista will already have a market share of at least 7.38%, or even higher, a percentage illustrative of some 70+ million licenses sold worldwide. And in this regard, it still remains to be seen if Leopard will take a bite out of Vista.