There are more signs that, at least in theory, the dominance of Microsoft's (NASDAQ:MSFT) Windows operating system may be slightly less potent than, say, a year ago this time. CNET and other news outlets reported today that AT&T (NYSE:T) is at least consideringApple's (NASDAQ:AAPL) Macintosh and Linux's operating systems for its corporate desktops.

AT&T may be showing signs of being a big corporation that's thinking out of the box, but for now, this is just a peek and little more than that. After all, it's just an evaluation, and according to the article, the decision will hardly be snappy: AT&T will decide on its OS of choice by the end of next year or early 2006.

Although early 2004 swirled with news of serious security issues becoming Microsoft's Achilles heel, not to mention the standard perception that Windows is too expensive for many customers, particularly those in emerging markets, Microsoft has shown signs that it's well aware of open-source and other threats.

Cases in point: Microsoft's stripped-down, inexpensive version of Windows for Asia, and recent word it will reveal some more of its source code to government clients. It also talks a good game about attacking the security issues, though whether or not other technology companies will necessarily play ball may be a good question after a recent experience with Time Warner's (NYSE:TWX) AOL.

Last May, research firm Gartner predicted that this year and next would herald a tidal wave of PC upgrades, what with an improving economy and the fact that there are still plenty of Y2K-era computers floating around out there. Microsoft's expiring support for older versions of its operating system was also indicated as playing a part in the upgrade cycle. However, since then, Gartner did ratchet back its prognostications for PC sales somewhat, and of course, economic indicators have recently given some mixed signals.

If today's news says anything at all, though, it's that corporations are becoming aware that there are alternatives to Windows, as well as reasons to consider them (and that Linux and Apple have come a long way and are now alternatives to those other than fanatics, geeks, and hobbyists). And when there are viable, compatible options, and some questions about the status quo solution, indeed, it would be remiss for corporations to ignore them. Apple investors, as well as the variety of corporations betting on Linux, may have some reason for cautious optimism.

Fools are talking about the news on the Apple discussion board. Or, if you're a Linux user, you might want to check out our Linux User's Group.

Alyce Lomax does not own shares of any of the companies mentioned.