SAN FRANCISCO — If fewer people are interested in buying a new personal computer, then fewer investors want to own stakes in companies whose fortunes are tied to the sales of laptop and desktop machines.

That logic ruled Thursday as Wall Street reacted to fresh evidence that PCs are turning into a dying breed of technology as consumers and businesses embrace smartphones and tablet computers as their preferred computing devices.

The stocks of PC software maker Microsoft and PC maker Hewlett-Packard absorbed significant hits on the news that PCs suffered an unprecedented sales decline during the first three months of the year.

Other companies connected to the PC industry, such as Intel, also were affected, although not to the same degree as the industry bellwethers.

First-quarter shipments of PCs plummeted by 11 percent to 14 percent from a year earlier, according to separate estimates issued late Wednesday by Gartner Inc. and International Data Corp.

By either measure, it was biggest decrease recorded by either research firm since they began tracking PCs sales.

For IDC, the data goes back to 1994, just before Microsoft released a revamped PC operating system called Windows 95, which played a major role in triggering a sales boom that turned laptop and desktop machines into a household staple.

Microsoft hoped to revive PC demand last year with the debut of the most dramatic makeover of Windows since the 1995 redesign. The changes imbued Windows with some of the qualities of mobile software, including touch-screen controls and a display of applications in a mosaic of interactive tiles.

Although Microsoft said it’s happy with the more than 60 million copies of Windows 8 that have been sold since its October release, analysts have been disappointed.

In its report, IDC blamed Windows 8 for accelerating the sales decline by confusing too many people who had become accustomed to using the old operating system.

Another problem: The PCs designed to run on Windows 8 are coming in a befuddling array of styles and are demanding significantly higher prices than older models, at a time when the initial out-of-pocket expense for a smartphone is as low as $99 and tablet computers go for less than $200.