On linux, files starting with . (dot) are hidden. They are by default not shown by file managers etc. Usually, they are configuration files and other stuff you don't need to see all the time.

But..... On N900, the folders you see in the default file manager as "Audio Clips", "Images" and all those that have nonstandard icon, are actually hidden folders on the file system called .sounds, .images and so on. Reason given is so that they could localize the names. IMHO they really screwed it up. I'll have to make some workaround for this in the future, because people can't access their data through hidden files and although its possible to move these directories, I think its not easy and you can't expect that from regular users.

So, press Ctrl-H to show these files starting with a dot and you'll find all your data in those ugly-named directories.