Saw someone else post same thing, I misunderstood what they were talking about. http://www.gnutellaforums.com/window...tml#post334647 Their post was off-topic any way.
After googling it, it seems it's a split part of a file. A little like how rar archive file can be split into different parts during compression. Likewise there's similar splitters for music & video & text files, etc. You might just have one part of the split file, or the part a, but missing the other parts.