How do I permanently remove files from my computer?
Answer: You may not realize it, but when you delete a file on your computer, it is not completely erased. Instead, the pointer to the file in your computer's file system is removed. Therefore, it may be possible to recover deleted files from your hard drive using a file recovery utility.
If you want to permanently remove files from your computer for security purposes, you can use a "file shredder" utility that overwrites deleted files. This type of program will write random bits in place of deleted files, making it impossible to recover the data.
If you want to overwrite all deleted files in one fell swoop, you can select an option that says, "Wipe free space" or something similar. This will overwrite the unused portion of your disk with all zeros or random data.