As RTO stated, even though you may have deleted a file to the recycle bin, and then emptied the bin, it's not really gone at all. It is a very simple job to recover the file from the hard disk (using a program such as Norton undelete).
The only way to totally delete any file, is to ensure that once the file has been deleted, the space on the hard drive it occupies is overwritten. There are a few progs available that totally overwrite the free space on your disk. (I've found "cyberscrub" to be very good).
419