Are you sure the files are actually gone? When you look on the computer are they no longer on the memory stick? Depending on what program you use to delete files they might still be there. For example, some psp programs can't delete read only files. Also, If your on a windows machine (I don't know how to view hidden files on any other OS) I would tell your folder settings to show hidden folders and see if there is anything hidden on there that you don't need.