After 2 years of examination the U.S Patent and Trademark Office has reversed its two earlier unofficial decisions and decided that Microsoft's File Allocation Table file system constitutes a "novel and non-obvious" system enabling it to be patented. The decision could allow Microsoft to go after open-source developers who use the technology. FAT controls how computers store information to hard drives and other storage devices such as Flash cards or MP3 players, or other devices that work with Windows.

The patents are part of Microsoft's implementation of a broader system for storing computer files. Microsoft did not claim control over the entire system, called File Allocation Table, or FAT, but rather a specific part that. However, the decision would theoretically give Microsoft a strategic weapon to attack Linux, at a time of its choosing.