You rarely hear about a new OS causing people to panic. But IT consultant Scott Pam says that's exactly what his small-business clients are doing when they install Windows Vista on new PCs and run smack into compatibility or usability roadblocks.

Pam's clients are not alone: Since InfoWorld launched its petition drive on January 14 to ask Microsoft to continue selling new XP licenses indefinitely alongside its Vista licenses, more than 75,000 people have signed on. And hundreds of people have commented -- many with ferocious, sometimes unprintable passion. "Right now I have a laptop with crap Vista and I'm going to downgrade to XP because Vista sucks," reads one such comment.

Where does all the vitriol come from?

IT managers and analysts suggest a range of reasons, some based on irrational fears and others based on rational reactions to disruptive changes.

Emotional effects

"When we first deployed Vista, people told us it sucks, that it's not as good as XP," recalled Sumeeth Evans, IT director at Collegiate Housing Services, an 80-person college facilities management firm. A month later, he surveyed the staff to see if their views had changed, and they had: "They said it was very good, that they were getting used to it. We asked what was different, and they said they originally didn't like Vista because it was a change. That's human nature."

Microsoft's overzealous schedule in replacing XP with Vista has exacerbated resistance to change, said Michael Silver, a research vice president at Gartner. The company had originally planned to discontinue XP sales on Dec. 31, 2007, just 11 months after Vista was made available to consumers and 14 months after it was made available to enterprises. The date for new license sales to end is now June 30.

In practice, XP's consumer availability ended for many users even sooner -- just six months after Vista's release -- since storefront retailers Best Buy and Circuit City and most computer manufacturers' Web sites stopped selling XP-equipped computers in July 2007. Typically, Microsoft has given customers two years to make such a transition, Silver noted.

Burton Group executive strategist Ken Anderson suggested that the strong emotional identification with XP represented a fundamental shift in how people, including IT staff, now think of operating systems. They have become a familiar extension of what we do and how we work, thus not something want to change often. "When technology becomes part of you, you don't want people to mess with it," he said.

Anderson likened the reaction to XP's impending demise to what happened in the 1980s when Coca-Cola replaced its classic Coke formula with New Coke, causing massive protests by customers who had no reason to change what they drank. The protests forced the company to bring back what we now call Coke Classic. "XP has come to the point of being Coke Classic," he said, with Vista playing the role of New Coke.