U oni do that for external devices like thumbdrives, external
hardisks, mp3 player and other external peripherals. If u drag and
drop the files into the trash bin and clear it... that's it.
Data from the thumbdrive will oni be deleted if u drag the files
FROM the thumbdrive to the trashbin and thrash it. It will not
delete any data if u jus D&D the thumbdrive icon.
BUT dun do that to your onboard Hardisk hor! 
