All of my USB sticks now have contain a file named
syncguid.dat. They began to appear when I bought a new HP Mini Note and I assume they are created by some of the bundleware that came with it.
But now I'm concerned that it could be malware. I couldn't find much using Google even when I added "HP" and "Mini Note" to the search terms.
(There seems to be no other questions of this type on Superuser.com but the FAQ doesn't say anything against it so let's give it a try)
It is a
JSON file with the following format (x represents a hexadecimal digit)