In April, the Public Patent Foundation asked the U.S. Patent and Trademark Office to that covers the FAT (File Allocation Table) file system--the older of two main systems used by Windows to store files. Last year, Microsoft said it was seeking to on reasonable terms as part of a broader push toward sharing its intellectual-property portfolio with the industry.
The FAT file format has become a common means of storing files not just on computers but also on removable flash memory cards used in digital cameras and other devices. It is also used by the open-source that lets Linux and Unix computers exchange data with Windows computers, and by Linux itself to read and write files on Windows hard drives.
"This is the first step toward ending the harm being caused to the public by this patent that should have never been issued."
--Dan Ravicher, founder
of the Public Patent Foundation
Some have worried that Microsoft may claim that Linux infringes on Microsoft patents and will seek a royalty. Any monetary compensation could threaten the operating system, which under General Public License (GPL) terms may not be distributed if it contains patented technology that requires royalty payments.
The foundation issued a statement applauding the review.
"We are obviously very pleased with the Patent Office's decision to grant our request to re-examine Microsoft's FAT patent," group founder Dan Ravicher said in the statement. "This is the first step toward ending the harm being caused to the public by this patent that should have never been issued."
Microsoft said on Friday that it is confident in the validity of its patents.
"At this point, we have the opportunity to demonstrate why this file system innovation deserves patent protection," David Kaefer, director of Microsoft's intellectual property and licensing group, said in a statement. "The USPTO often grants re-examination requests, and they provide an important mechanism to assure high levels of patent quality."
The foundation pointed out that third-party requests for re-examination like the one filed in this case are successful at having the subject patent either narrowed or completely revoked roughly 70 percent of the time. About 12 percent of patents are ruled invalid, while 58 percent are narrowed, and 30 percent upheld, according to USPTO statistics.
CNET News.com's Stephen Shankland contributed to this report.