Are you using an old OS (pre OS X)?I may be wrong, but I seem to remember that files pre OS-X were made up of 2 parts, data & resource, Windows will see 2 files and not understand either of them.
(
printmeister http://tinyurl.com/c8s8fd5 for titanic T's,
Sun 6 Dec 2009, 10:52,
archived)
What used to happen was that when you sent a file over a network it only sent the data and not the resource forkso image files were alright, though when you got them back again the mac might not know what the filetype was (unless some program had set the resource fork up again, like a web browser would when you save an image).
(,
Sun 6 Dec 2009, 12:14,
archived)