A safe and secure method is compulsory to delete important file permanently.. You should keep in mind that the data deleted even decades can be restored very safely so the deleted bank account details, secret pins, information and codes can be easily retrieved. Kernel file shredder is the best utility which deletes the information in such a way that it can never be recovered back. This data eraser tool can erase all types of files such as documents; excel sheets, zipped, JPEG, Presentation etc. at a time. You can download this software from here http://www.deletefile.org/