Are sales of personal computers coming out of their recent tailspin and finally recovering, or is it all just a Microsoft-induced mirage?

Most analysts, especially the ones that follow PC-making companies, seem to think a rebound is imminent. But a few contrarians warn that Microsoft’s (MSFT) move to stop supporting the ancient Windows XP system after April fueled a temporary upturn, one that likely will soon disappear.

So far in 2014, PC sales have been much healthier than over the past three years, giving a boost to major tech companies including Lenovo (0092.HK), Intel (INTC) and Hewlett-Packard (HPQ), which reports its fiscal third quarter earnings after the market close Wednesday. Lenovo's Hong Kong-listed shares are up 30% in 2014, while shares of Intel have risen 33%, and HP shares, which doubled last year, have gained another 26%.

HP CEO Meg Whitman has impressed investors with her turnaround efforts, but most of the company’s recovery thus far has been thanks to job cuts, expense reductions and generally smarter balance sheet management. Finding avenues of real growth has been more elusive. Wall Street will be looking for signs of further progress later on Wednesday.

The big decline of HP and its ilk came as PC shipments dropped almost 1% worldwide in 2011, 4% in 2012 and nearly 10% last year, according to Gartner. But last quarter the decline was back below 2%, Gartner said.

Splendiferous tablet sales, led by Apple’s (AAPL) iPad, took quite a bite out of PC sales, as did corporations tightening up on IT spending after the 2007 to 2009 global recession. Consumers, meanwhile, have delayed replacing “good enough” computers and paid far more attention to upgrading their smartphones.

A burst of activity

But back in 2012, Microsoft sowed the seeds of a minor burst of PC replacement activity. The company announced that, as of April 8, 2014, it would be terminating all support – everything, even security upgrades -- for Windows XP, at that time the world’s most popular operating system. By some estimates, half of all corporate PCs were running XP at the time.

Windows XP’s market share has since declined to 25% to 15%, depending on how you measure it, but what’s left is increasingly among consumer PCs that aren’t likely to ever be replaced, at least not by another PC.

All those replacements bolstered sales at companies such as HP, which reported an 8% increase in revenue from its personal systems group last quarter and a 4% gain the prior quarter. Analysts expect another modest increase for the most recent quarter. And the sages at Gartner see PC sales actually increasing worldwide next year by a modest 3%.

Some have confused the slowdown in tablet buying, which saw a market increase of just 5% last quarter according to Strategy Analytics, with an uptick in PC buying. But the two trends likely aren’t related at all.

As tablets spread quickly from early adopters to regular consumers, the rate of replacing and upgrading devices has slowed dramatically. And the most recent tablet upgrades from Apple, Samsung and others, while plenty cool, haven’t fundamentally altered consumers’ perceptions. People aren’t forgoing tablets to buy PCs – they’re just replacing tablets at a slower rate.

Still, some companies that have already reported for this quarter have argued that the replacement cycle has a long way to go. "The installed base of PCs that are at least four years old is now roughly 600 million units," Intel CEO Brian Krzanich said on his call with analysts last month. "And we are seeing clear signs of a refresh in the enterprise and small and medium businesses."

HP’s earnings, and its executives' comments on their call with analysts, should provide more data points. Overall, analysts expect HP will report revenue of $27 billion, down 1% from a year ago, and adjusted earnings per share of 89 cents, three cents more than last year, according to FactSet.

But it will be HP’s guidance about the rest of the year that tech investors should pay attention to most closely. That could help reveal just how much higher the PC sales recovery can fly.