Of course, prognosticators perennially say Linux is on the verge. It gets high marks for security and stability and is widely used behind the scenes in corporate servers, making it a natural candidate to steal desktop thunder from Microsoft's dominant Windows. And yet Linux PCs still represent less than 2 percent of the market.

This time, though, there's actually evidence of momentum.

While the best features in the latest Windows release, Vista, require top-notch configurations that can quickly ramp up a PC's price, one of the hottest segments of the industry involves inexpensive computers.

Laptops under $400 are real possibilities now, and some of the most buzz-worthy use Linux, such as Asustek Computer Inc.'s EeePC and the One Laptop Per Child Foundation's $200 "XO" computer for schoolchildren. Linux also is available on slim little "netbooks" being pushed by Intel Corp.

Not only is Linux essentially free to the PC vendor, but the operating system also is better suited than Vista for cheap PCs' spartan hardware designs. (Windows XP is available on scaled-back PCs like Intel's Classmate, but it's unclear what will happen after Microsoft soon stops selling XP to the general public.)

Linux might benefit from a changing conception of what computers are for. With the rise of Web-based applications that reduce the need for desktop-bound software, more of the action comes through an Internet browser now. The feel of the underlying operating system is less important.

That means Linux consumers can get a lot out of their computers even if they are put off by what many reviewers still cite as Linux's biggest flaw: its uneven user-friendliness. Some tweaks to Linux machines require higher-than-average computing savvy, although this is less of an issue than in the past.

Perhaps more importantly, if the desktop operating system fades further into the background, PC makers could have greater incentive to save money on it by offering Linux.

The price that big PC manufacturers pay Microsoft for Windows varies and is not disclosed, but is believed to commonly exceed $50 per PC.

"I'm a big believer in the inevitable forces of economics - they're like glaciers," said Mark Shuttleworth, CEO of Canonical Ltd., which this month is releasing a new version of Ubuntu, a leading version of Linux that can run PCs. "Glaciers carve out terrain. It takes time."

Linux on the desktop doesn't have to take off like crazy to really start to matter. Of the 981 million PCs in existence worldwide last year, 1.7 percent ran Linux, according to Gartner Inc. That sounds paltry. But Apple's Mac operating system accounted for just 2.5 percent, and Apple is considered a significant, influential alternative to Windows.

"Every point is billions of dollars to Microsoft," says Jim Zemlin, head of The Linux Foundation, a consortium devoted to advancing Linux.