i have a usb/pen drive i bought from ebay. when i copied files it took two or three times copying them to get good files on it/same file size. some folders would will copy with no files and some files will copy. I made a new folder and have thesame trouble copying files.....in addition whenever i unmount (exlporer/eject/..safe to remove...) the drive and remount the last folder always comes back mty. files in root come back in tact. Not a whiz kid on the pc...but i know some and this is confusing. no problems with local purchased drives