Twenty-one months after its initial release, what do we know about Windows Vista? That home users hate it, businesses are uninstalling it and - according to Gartner - it's proof that the 23-year-old Windows line is "collapsing" under its own weight.

Meanwhile, predecessor Windows XP, which Microsoft stopped shipping to retailers and the major PC makers on June 30, has belatedly become so beloved that it's garnering more calls for "unretirement" than NFL icon Brett Favre did in his wildest dreams this summer.

But all of the griping about Vista and instant nostalgia for XP covers up a dry, statistical reality: XP itself was slow to catch on with users - maybe even slower than Vista has been thus far. For instance, in September 2003, 23 months after its release, XP was running on only 6.6% of corporate PCs in the US and Canada, according to data compiled by AssetMetrix, an asset-tracking vendor that was later bought by Microsoft.

In comparison, Forrester Research reported that as of the end of June - 19 months after Vista's November 2006 debut for business users - the new operating system was running on 8.8% of enterprise PCs worldwide. Forrester analyst Thomas Mendel, who authored the report, wasn't impressed: He compared Vista to the ill-fated New Coke.

However, even Gartner, that prophet of Windows' doom, forecasts that Vista will be more popular at the end of this year than XP was at a similar juncture - with 28% of the PC operating system installed base worldwide, vs 22% for XP at the end of 2003.

"The uptake of XP was slower than people remember today," said Michael Cherry, an analyst at Directions on Microsoft in Kirkland, Wash. He noted that many IT managers "labelled XP a consumer-only upgrade" at first.

Users loved Windows 2000, which was less than two years old when XP was released (see story at right). And for many, XP didn't add enough to make them want to move up. "XP was really viewed as a glorified upgrade, not a new operating system in its own right," recalled Donnie Steward, CIO at ACH Foods, a Memphis-based maker of processed foods.

Then there were all the security issues. XP now is considered to be highly secure, but that wasn't the case in 2002. That's when LifeTime Products Inc. upgraded to the operating system after Microsoft released Service Pack 1, its first bug-fix update. John Bowden, CIO at the Clearfield, Utah-based maker of recreational equipment, noted that for years after it was released, XP received a "massive amount of criticism" for its lack of security. "We used to say XP was like Swiss cheese - full of holes everywhere," Bowden said.

To try to fix the security problems, Microsoft developed a second service pack, which it pushed customers to adopt. But there were two problems. First, not everyone was convinced that SP2 would be a security cure-all - a view that was partly vindicated by later developments.

And second, SP2 was such a major change that it broke applications - lots of them, especially enterprise ones.

"We consider XP SP2 to be a major release because of the nature of the enhancements," one IT manager told Computerworld in 2004. Such opinions prompted many companies to block updates to SP2 on their PCs for months until they could prepare for the mammoth upgrade.

Another Forrester report, by a different analyst, cites a "new trend" of upgrades from XP to Vista - and says that skipping Vista to wait for Windows 7 would be a mistake.

Some of the reasons cited for Vista's supposed doom are unique to the new operating system. There's the widespread exercising of downgrade rights by users who purchase PCs with Vista but then revert to running XP. Mac OS X has taken some market share away from Windows over the past year. Cloud computing technologies offer new competition. And the scheduled early 2010 arrival of Vista's successor, which Microsoft is calling Windows 7, looms on the horizon. Both Steward and Bowden said they will likely skip Vista entirely and wait for Windows 7.

But other strikes against Vista are ones that XP has also faced and overcome, such as a tottering economy (the dot-com bust, in XP's case), the belief that it was a piece of "bloatware," accusations of price gouging by Microsoft, and apathy or revolt by end users.

For most users, "change is always bad," said Merrie Wales, information systems manager in the human resources department in Glenn County, California. Wales, who oversees 250 desktop PCs, said that only a tiny portion of her users welcomed a move to Vista this spring. But, she noted, a similar sliver of users was happy when the agency finally upgraded to XP in 2006.

And the Vista rollout "has turned out much better than we anticipated," Wales said. "It's not a bad OS. There are big improvements under the hood."

There also are other factors that brighten the long-term outlook for Vista:

1) Virtualization is easing compatibility problems

Like Vista, Windows XP has an application compatibility mode that simulates older versions of Windows. But it's not perfect. And Vista gives more options to IT managers who are stymied by drivers or applications still breaking.

For instance, Glenn County runs Vista in standard mode, instead of administrator mode, on all of its PCs for security reasons. But the human resources department had a key application that could run only in administrator mode. To solve that problem, Wales said she used Microsoft's application virtualization technology to create a self-contained app package that runs as an administrator inside a virtual machine but doesn't require end users to possess admin credentials.

2) Deploying and managing Vista is easier

More advanced deployment tools and systems management software, from Microsoft and third-party vendors, combined with broader bandwidth, are making it easier for admins to press a button and remotely roll out Vista to new or existing PCs than it was in XP's hey day.

3) Things are finally lining up for 64-bit computing

PCs running 32-bit Vista don't sport a big performance advantage over XP systems. But 64-bit Vista PCs tricked out with dual- or quad-core processors, multiple terabytes of storage, up to 128GB of RAM and multiple video cards serving multiple widescreen LCDs - they, in short, do.

Such gear was out of reach of the typical user five years ago. More importantly, little software, especially games, had been ported to be compatible with 64-bit technology, much less take advantage of its power. It was the typical chicken-and-egg problem. As a result, 64-bit never really caught on with XP, despite Microsoft's exhortations.

With Vista, 64-bit appears to be finally catching on among more than just technology enthusiasts. Microsoft claimed last month that 20% of new Vista PCs in the US appear to be 64-bit, compared to just 3% in March. That kind of uptake may finally drive software vendors to port their Vista apps, especially high-performance ones, to the 64-bit versions of the operating system.

In addition, history tends to repeat itself. XP deployments eventually accelerated, reaching near-ubiquity by the time Vista finally debuted. Similarly, some industry observers expect rollouts of Vista to pick up - even in the shadow of Windows 7 - as a Vista SP2 arrives, companies refresh aging hardware and the end of mainstream support for XP next April draws closer.

For instance, Gartner expects Vista to be running on 49% of all PCs worldwide by the end of next year - surpassing XP's market share, which the consulting firm forecasts at 44%.

Lundberg Family Farms in Richfield, California, is in the process of upgrading its 100 PCs to Vista. "We don't try to be at the cutting edge, but we don't want to be too far behind," said Todd Ramsden, Lundberg's IT manager. "Sooner or later, we knew we were going to have to move forward."

Ramsden added that his users have been "pretty good with going with the flow" on the rollout. "I've gotten some complaints about Vista," he said. "But most of the time, it turns out they're really complaining about some change in Office 2007."

Moreover, most of the talk among enterprise Vista holdouts is about sticking with XP or waiting for Windows 7 - not switching to Mac OS X or Linux. Cherry said skipping an operating system release may merely be a long-term trend, not an indication "of Vista being a failure." And he noted that until companies jump off the Windows treadmill instead of merely slowing it down, "Microsoft still makes its money."

Vista's challenges echo those of Windows XP

Early opinions of Windows XP were remarkably similar to those that many users offer about Windows Vista today.

For instance, a Computerworld survey of 200 IT managers conducted in the fall of 2001, just before XP was released, found that 53% of the respondents didn't plan to upgrade their PCs, while another 25% were undecided. And in an informal poll of 25 users a year later, only four said they had started deploying XP.

"We have not moved to XP, and we have no plans to," one CIO said in 2002. "This is an upgrade that offers nothing to a business customer."

Another IT manager said that the cost of upgrading to XP was "very high" and that there wasn't "a lot of perceived value" in moving up.

Many companies had just finished or were still rolling out Windows 2000 when XP came along just 20 months after its predecessor. Few could get excited at the prospect of another upgrade, especially when the economy turned sour after the dot-com bust.

And although XP may seem svelte compared with Vista, at the time, it was considered by many to be a bulky resource hog that likely would bog down applications on older PCs.

As of March 2005, Windows 2000 was still running on almost half of business PCs in the U.S. and Canada, according to usage data compiled by asset-tracking vendor AssetMetrix prior to its acquisition by Microsoft.

"Vista really does parallel the situation with XP in a lot of ways," said Michael Cherry, an analyst at Directions on Microsoft.