Drive wiper will overwrite the diskspace where a file was with 0's and 1's to make it more difficult to recover a deleted file. It takes time and is not needed unless you have "for the president eyes only" files that are deleted on your system :-) Besides, all those wiping utils only make it harder to recover a deleted file, but there are companies that are able to recover over 99.99% of deleted files. For normal users there is no need to wipe space.