If you have Mac OS X, you may realise that it creates small mirrors of each file, such as if you have song.mp3, a ._song.mp3 is also created. While this is a little problem on Mac OS X, other OS pick this file up as another, corrupt file(such as the PSP). There is a way to sweep these files away, with a simple console command.
This will remove all ._, .DS_Store files quickly and easily. In this case my Memory Stick was called "MMS". Replace MMS with the name of your Memory Stick for this to workCode:dot_clean /Volumes/MMS
This is a console command, as always be careful in what you do in the Terminal
Here's the man page for those who :rtfm::
Spoiler for Man Page: