Microsoft Corp.'s operating systems run most personal computers around the globe and are a cash cow for the world's largest software maker. But you'd never confuse a Windows user with the passionate fans of Mac OS X or even the free Linux operating system. Unless it's someone running Windows XP, a version Microsoft wants to retire.

Fans of the six-year-old operating system set to be pulled off store shelves in June have papered the Internet with blog posts, cartoons and petitions recently. They trumpet its superiority to Windows Vista, Microsoft's latest PC operating system, whose consumer launch last January was greeted with lukewarm reviews.

No matter how hard Microsoft works to persuade people to embrace Vista, some just can't be wowed. They complain about Vista's hefty hardware requirements, its less-than-peppy performance, occasional incompatibility with other programs and devices and frequent, irritating security pop-up windows.

For them, the impending disappearance of XP computers from retailers, and the phased withdrawal of technical support in coming years, is causing a minor panic.

Take, for instance, Galen Gruman. A longtime technology journalist, Gruman is more accustomed to writing about trends than starting them.

But after talking to Windows users for months, he realized his distaste for Vista and strong attachment to XP were widespread.

"It sort of hit us that, wait a minute, XP will be gone as of June 30. What are we going to do?" he said. "If no one does something, it's going to be gone."

So Gruman started a Save XP Web petition, gathering since January more than 100,000 signatures and thousands of comments, mostly from die-hard XP users who want Microsoft to keep selling it until the next version of Windows is released, currently targeted for 2010.

On the petition site's comments section, some users proclaimed they will downgrade from Vista to XP - an option available in the past to businesses, but now open for the first time to consumers who buy Vista Ultimate or Business editions - if they need to buy a new computer after XP goes off the market.

Others used the comments section to rail against the very idea that Microsoft has the power to enforce the phase-out from a stable, decent product to one that many consider worse, while profiting from the move. Many threatened to leave Windows for Apple or Linux machines.

Microsoft already extended the XP deadline once, but it shows no signs it will do so again. The company has declined to meet with Gruman to consider the petition. Microsoft is aware of the petition, it said in a statement to The Associated Press, and "will continue to be guided by feedback we hear from partners and customers about what makes sense based on their needs."

Gruman said he'd keep pressing for a meeting.

"They really believe if they just close their eyes, people will have no choice," he said.

In fact, most people who get a new computer will end up with Vista. In 2008, 94 percent of new Windows machines for consumers worldwide will run Vista, forecasts industry research group IDC. For businesses, about 75 percent of new PCs will have Vista. (That figure takes into account companies that choose to downgrade to XP.)

Although Microsoft may not budge on selling new copies of XP, it may have to extend support for it.

Al Gillen, an IDC analyst, estimated that at the end of 2008 nearly 60 percent of consumer PCs and almost 70 percent of business PCs worldwide will still run XP. Microsoft plans to end full support - including warranty claims and free help with problems - in April 2009. The company will continue providing a more limited level of service until April 2014.

Gillen said efforts like Gruman's grass-roots petition may not influence the software maker, but business customers' demands should carry more clout.

"You really can't make 69 percent of your installed base unhappy with you," he said.

Some companies - such as Wells Manufacturing Co. in Woodstock, Ill. - are crossing their fingers that he's right. The company, which melts scrap steel and casts iron bars, has 200 PCs that run Windows 2000 or XP. (Windows 2000 is no longer sold on PCs. Mainstream support has ended, but limited support is available through the middle of 2010.)

Wells usually replaces 50 of its PCs every 18 months. In the most recent round of purchases, Chief Information Officer Lou Peterhans said, the company stuck with XP because several of its applications don't run well on Vista.

"There is no strong reason to go to Vista, other than eventually losing support for XP," he said. Peterhans added that the company isn't planning to bring in Vista computers for 18 months to two years. If Microsoft keeps to its current timetable, its next operating system, code-named Windows 7, will be on the market by then.