Two major computer corporations, Intel and Netscape Communications, have announced investments in a small company developing the Linux operating system - seen as a long-term threat to the dominance of Microsoft's Windows.
Red Hat distributes and supports versions of Linux including one that resembles the graphical user interface of Windows.
But Linux is regarded as more stable than Windows by its proponents and is available free over the Internet.
Red Hat and a handful of other companies apart, Linux lacks proper commercial support.
But, unlike Windows, the code of the operating system is open to all and fixes to problems are rapidly developed by a worldwide user base now eight million strong.
Big corps replace esprit de corps?
Once the preserve of self-confessed nerds, Linux is being turned into a product suddenly being supported by major companies, many of them in the anti-Microsoft camp.
Caldera and Oracle, both at loggerheads with Microsoft, have announced Linux versions of their products. Netscape and Intel's move may also be seen as a strike at Bill Gates.
But Intel's interest appears to run deeper. A principal engineer told a Linux seminar this month that many members of staff used it as their desktop development system.
He said Intel was planning support for Linux on its advanced 64-bit Merced chip at the same time as it supports Windows NT.
Microsoft see Linux as rival
In a submission to the Securities and Exchange Commission on Friday, Microsoft said it expected more competition from rivals such as Linux.
"Over the past year the Linux operating system has gained increasing acceptance, and leading software developers such as Oracle and Corel have announced that they will develop applications that run on Linux," it said.
Linux is a version of the UNIX operating system that runs on Intel-based PCs and Internet servers.
It was developed by a Finnish computer scientist, Linus Torvalds, and has been fostered by the Internet community along with other freeware such as Apache, the most popular server software for Websites.
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