Microsoft\u2019s first major operating system upgrade in five years, Windows Vista, is expected to hit the retail shelves in January. Originally scheduled for 2003, Vista\u2019s release date was pushed back many times due to development delays. And the delays have created openings for the growth of competitors, such as Apple on the desktop and Linux on the server. But Microsoft\u2019s market share remains overwhelming. Like it or not, Vista will eventually become Microsoft\u2019s default OS. So the question is not whether you\u2019ll be making the switch to Vista, but when.In fact, if your company has a volume licensing agreement with Microsoft, you\u2019ll have a chance to upgrade to the client version of Vista as early as November, when the operating system will be shipped to computer manufacturers and other large customers. (The server version of Vista, still nicknamed Longhorn, isn\u2019t scheduled to ship until 2007.)Still, there are good reasons why IT managers are saying "wait and see." Upgrades are time-consuming and expensive, requiring lots of testing, training and support. Then there\u2019s the hardware. Vista\u2019s almost certainly not going to run well on older machines. "IT managers probably won\u2019t make the investment [in upgrading] until after Vista has been on the market for awhile," says Jim Michael, secretary of the board of directors of Share, an IBM users\u2019 group with more than 2,000 member companies representing a majority of the Fortune 500. "You may not see widespread enterprise deployment until after the first service pack comes out." And that could be as much as a year after Vista first ships.But you\u2019d better begin planning now. Once the OS is widely available, end users (like your CEO) will start asking about it. It will begin showing up on new desktops and laptops. And, if there\u2019s a major security attack aimed at legacy Windows XP systems, you could find yourself under very serious pressure to upgrade fast. Security and ManageabilityVista offers some enticing features for CIOs. Perhaps primary among them are its numerous security enhancements. "This is an operating system that was built and architected in the age of the Internet," says Michael Gartenberg, VP and research director for JupiterResearch. In contrast to Windows XP, Vista will be much more resistant to Internet-based attacks, he says. Vista also offers authentication via smart cards in addition to user name and password checking, provides more nuanced user account restrictions and offers strong, hardware-based encryption, which can protect documents when an employee\u2019s laptop is stolen. It will also make it easier for developers to customize their own authentication strategies with biometrics and tokens.Almost equally important are Vista\u2019s management features. "Vista will help ease the pain of deploying, supporting and managing desktops," says Michael Burk, a product manager in the Windows client division of Microsoft. Microsoft claims that administrators will be able to control desktop settings remotely via command line, eliminating the need for your IT staff to visit every desktop when, for instance, it\u2019s time to upgrade client virus-scanning software. To streamline installation, Vista will ship with a suite of disk imaging and installation tools so IT departments can configure standard installations easily and then copy them onto new computers with a minimum of fuss.A Shiny New InterfaceVista\u2019s new interface and multi\u00bfmedia features may be the system\u2019s most visible enhancements. Windows XP is looking a little long in the tooth, and Vista\u2019s new Windows Aero interface is a lot slicker (and a lot more Mac-like), with transparent windows and a variety of 3-D effects.All those effects require fairly serious graphics processing power. However, there\u2019s an option for systems with slower video subsystems. If a PC\u2019s graphics processor can\u2019t handle Aero, the user can turn it off, defaulting to a plainer but less resource-intensive interface. Still, it\u2019s unlikely that the new interface is going to be a major factor in a CIO\u2019s decision to upgrade. "OK, so it\u2019s a cooler-looking Windows interface. I\u2019m not sure where the big payback for the enterprise is for a cooler-looking Windows interface," says Share\u2019s Michael.Two for the BusinessWindows Vista will ship with two business-oriented versions: Windows Vista Business and Windows Vista Enterprise. "Windows Vista Business edition is optimized for small to medium-sized businesses, but it\u2019s designed to meet the needs of organizations of all sizes," says Microsoft\u2019s Burk. Vista Business will include IT management tools, end user search tools for organizing and sorting through large quantities of business documents, and Tablet PC support.Vista Enterprise is aimed at larger organizations and adds enhanced application compatibility tools, disk image management tools (for creating and distributing standard installations), and the ability to run Unix applications on Vista PCs. Vista Enterprise will be available only to corporate customers that are enrolled in Microsoft\u2019s Software Assurance program or a Microsoft Enterprise Agreement.Proceed with CautionIf there aren\u2019t compelling business reasons to make the switch to Vista in 2006, consider putting it off. Alternatively, you can let Vista creep into your enterprise gradually as you buy new systems that have the OS preinstalled, recommends Rob Enderle, principal analyst for the Enderle Group. One reason for taking it slowly is that Vista\u2019s hardware requirements are steeper than those for Windows XP, and that means a lot of your old computers won\u2019t have enough horsepower to handle it. Although Microsoft has published its requirements list for Vista, Enderle has compiled his own list (see "Vista Systems Requirements," at right). But, he acknowledges, "the ideal hardware will be designed for Windows Vista\u2014and that won\u2019t show up until the fourth quarter of this year."Even if you\u2019re not planning on installing Vista for a year or more, you still should pay attention to its hardware requirements. "Anyone who\u2019s buying hardware this year needs to consider getting hardware that\u2019s sufficient for Windows Vista," says Ann Westerheim, president of Ekaru, a technology service provider for small and midsize businesses. That\u2019s because the typical corporate PC has a three-year lifespan, and over the next three years, you\u2019ll almost certainly need to run Vista.And don\u2019t underestimate the amount of work an operating system overhaul can require in a large enterprise. "Those of us who have done it will tell you it\u2019s never painless," says Jeff Reed, CTO of Logicalis, an enterprise IT service provider.Time to Get ReadyNow is the time to start learning about Vista by studying the product details that Microsoft has published on its main site and on the Microsoft Developer Network site (see msdn.microsoft.com\/windowsvista). If you can get into Microsoft\u2019s beta program, you will gain firsthand experience with Vista and, even more importantly, can begin testing its compatibility with your company\u2019s key applications. Once the OS ships, you want to be prepared with an upgrade plan\u2014and you will be upgrading, sooner or later."It\u2019s a question of whether you want to deal with a bunch of patches and fixes for XP when you can get everything that\u2019s already incorporated into Vista," says Gartenberg. Microsoft says it will continue to maintain Windows XP and is planning to issue Service Pack 3 for XP in the second half of 2007, but the trend is clear: Vista is coming and will eventually replace XP.The pressure will only increase in January, when (or if) Vista hits retail shelves. "Right now, Windows XP, with all its foibles, is working OK. IT managers are not chomping at the bit to rip the thing out by the roots," says Enderle. "But that could change dramatically once this thing ships."