The QuickTime file format created by Apple allows to manage in one single unit a great number of resources of very different kind, like sounds, still or moving pictures, and the like. The QuickTime (QT) movies are generally read by a special reader program (QuickTime Player), but there is a SDK and an API allowing developers to use freely (and abuse) the file format.
The QT file format is based on atoms. Those atoms can hold data, or other atoms. Those atoms exist in two flavours, the plain (old-style) atom and the QT (newer) atom. On the Macintosh, only one atom is stored in the resource fork of the file, the "moov" atom. The other ones are in the data fork, or in other data files. On the PC, all atoms must be in the same filestream (those files are called flattened files).
When you want to transfer QuickTime movies from the Macintosh to the PC, one first solution is to copy the data fork first, to a file with the mov extension, then the resource fork, to a file with the qtr extension (QuickTime Resource). The player reads the mov file and looks for the qtr file when it doesn't find the moov atom. The main problem of this solution is that both files must remain together in the same subfolder.
Obviously, it would be fine to be able to flatten the movie files when they are copied from a Macintosh medium to the PC hard disk.
Please note that, against the affirmations by some autoproclamed gurus, File Exchange (née Pc-Exchange) doesn't flatten the QuickTime movies when copying toward a PC disk.
The only solution I know for now is to open the movie in Apple QuickTime Player (version 4) and to save it under another name (item 'Save As' in the 'File' menu). Caution, the 'Make movie self-contained' option is greyed as long as you don't give another name to the file. The file is then flattened and you can delete the original files.
To overcome this cumbersome process, we developped a free utility, called QT-Flattener.exe (length 841 032 bytes). It can run on MacBinary files and on bundled files (data fork in a MOV file, resource fork in a QTR file). A 32-bit console version (length 97 117 bytes) is also available. It is not so heavy (no installer) and can run in a batch file.