Defrag of big video file

Windows XP Pro.

File dn008.0318.mp4 had been downloaded from democracynow.com by Miro.exe.

451,294 KB, about 6,264 fragments.

Windows defrag couldn't defrag it (or severals other video files.) Piniform defraggler showed 3 fragments after defragging it, but the message window said:

"defrag complete, no files were defraggmented."

Analysis confirmed file as having 3 fragments. The file played correctly in Quicktime media player and other players.

Please help me understand:

Q1 - How can a file become so fragmented?

Q2 - Why can windows not defrag it but Piniform Defraggler can defrag it?

Q3 - Why does Defraggler say that no files were defraggmented?

Information will be appreciated,

Stan Hilliard