Microsoft FAT patent rejected
 

Microsoft's attempt to create a lucrative future revenue stream from its patent portfolio has tripped at the first hurdle. After an appeal, the US Patent Office has struck down Microsoft's '517 patent (USPTO 5,579, 517) on the FAT file system. Camera makers, amongst many other consumer electronics manufacturers, use the FAT file system on compact flash cards and other removable media.

Microsoft introduced FAT in version 2.0 of MS-DOS in 1982, but was not granted patent '517 until 1996. Last year Redmond used it as the basis of its first ever licensing program, offering manufacturers the right to use the ubiquitous file system in return for a low royalty rate. At the time, Microsoft described this as "liberalization". Industry watchers noted how earlier in the year, Redmond had hired Marshall Phelps, the IBM attorney who in the Eighties, built up Big Blue's IP program from nothing into a multi-billion dollar business.

http://www.theregister.co.uk/2004/09...tent_rejected/

U.S. Patent filing is not an easy task.:)
Trust me.:D