More than 75,000 people have signed InfoWorld’s “Save XP” petition in the three weeks since it was launched — many with passionate, often emotional pleas to not be forced to make a change. On June 30, Microsoft plans to stop making new licenses to Windows XP available through most outlets, though business users and some consumers will be able to “downgrade” to XP after that date under certain circumstances. InfoWorld expects to present the petition to Microsoft when it has collected 100,000 signatures.

[ Follow all the coverage of and reader reaction to the “Save XP” campaign. ]

Although InfoWorld’s campaign has given a voice to users who prefer to keep the familiar XP, concerns over Vista had been bubbling since its release a year ago. That has been evident not only anecdotally in comments that InfoWorld editors have heard from IT staff and users alike, but also in the slow adoption of Vista in the marketplace.

While millions of people have gotten Vista with a new PC, most did not have a choice of what OS was loaded on it, since retailers stopped selling new XP computers in spring 2007 and online sellers (with the recent exception of Dell) made XP available only to business customers.

Where people have had a choice, Vista has not been it. Microsoft has reported that it sold 100 million Vista licenses in 2007, which means that roughly four out of 10 new machines shipped with Vista on them. By comparison, nearly 70 percent of PCs shipped with XP in its first year. According to NetApplications, about 11 percent of installed machines use Vista, compared to 75 percent running XP.

IT consultant Dimension Data Americas has yet to have any of its midsize business customers convert to Vista, said Jeff Dimock, its vice president of Microsoft solutions — though he noted that several are working on plans to do so. “The mid-market has not been upgrading to Vista,” said Karen Hayward, executive vice president at IT outsourcing firm CenterBeam, which provisions OS and other apps to midsize businesses.

Compatibility issues and lack of perceived value are the major reasons that businesses and users have avoided Vista. Research firm Gartner advises its clients not to switch to Vista until early 2009, after the first service pack has been released, third-party compatibility is improved, and more Vista-ready hardware is in the hardware purchase cycle, says Michael Silver, a research vice president at Gartner.