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Is there a program to truly delete all deleted files?
I am looking for a tool that wipes (overwrites) unlinked files; preferably something that runs as a kind of disk formatter, overwriting the entire unused portion of the harddrive partition while leaving everything else intact.
Ccleaner - check the Advanced option, Wipe Free Space.
Ccleaner is freeware, I recommend using the Portable or Slim version (the default installer will install a browser toolbar).
If you run Sysinternal's SDelete with the -z argument, it will cleanse free space on the given drive.
sdelete -z c:
This is a good solution if you want to run as a batch file every so often, or if you just prefer a command line tool.
