Hidden Files

So, my girlfriend has a CD with some files on it. Some of those files are set to hidden. Others are not. She said she couldn't read the files properly. I popped the disc into my Vista machine and voilà! There are all the files.

Thinking this is just a case of her computer isn't set to see hidden files, I take the disc over to her system and shove it in (triumphantly).

Moments pass by and I'm astonished... I change the settings to display hidden files... they're not showing up. I crack open the command prompt and I can see some files, but not all of them... All of the files set to hidden are... gone.

So, thinking it must be a fluke problem with her computer and permissions or something, I throw the disc back in my laptop and double click the drive...

...WTF... I can only see the files that are not set to hidden. I've made no changes to my computer between now and then. I have Kaspersky and it's up to date... no warnings of virus activity... Everything seems to be working, but those files are now gone!

I threw it into another system just to be sure, and it does the same thing... no hidden files on the disc.

So, I ask you this question... Where did they go?