The defrag people may be more interested in my DISKED program
(www.diskwarez.com/disked.htm) due to its code for parsing the FAT and
indexing all files (a linked list) to their allocated clusters.

I have been meaning to publish this data -- the algorithms may be of
interest you and defrag interested people. I just finished the FAT32
version a few weeks ago. 

My DISKED program can index all files (rather quickly) and then enable
you to associate a cluster to a file (full path name) or a file to all
of its clusters.

My license is such that you can take the DISKED file indexing code
(some algorithms and data structures) and integrate them into whatever
you want -- GPL code in your instance -- even without my [written]
permission. But in your case I could even provide help. It is up to
you.

Good luck and Peace
g jennings  