Microsoft's contentious patent which describes how to stick long filenames on FAT filesystems without breaking compatibility with old applications has been upheld by the German appeal court.

A prior court ruled patent EP0618540 invalid. In that case the German Federal Patent Tribunal claimed Microsoft had not actually invented anything. The Tribunal stated that the work done on the Rock Ridge Interchange Protocol, which allows long file names to be used on the ISO9660 filesystem used on CDs, solved the same problem. Rock Ridge was developed in 1991 and predates the FAT long file name work by a long way.

However the appeals court rejected this saying that there were technical differences between the two systems. Microsoft had to solve new problems that the Rock Ridge work didn't. These included the way long names on FAT were designed so that legacy systems would ignore the new names was deemed to be significant.

Microsoft wants to obtain license fees from companies wishing to use the FAT and FAT32 filesystems, which are an integral part of many embedded devices such as cameras and mobile phones.