Initialize Free Space: Confidential information is possibly stored in currently unused parts of a drive as a result of normal delete, copy and save actions. Free space on a drive can be initialized for security reasons. This effectively overwrites all data in unused parts of the disk and makes it impossible to recover this data. Available for partitions opened as drive letters. Available in WinHex only, not in X-Ways Forensics.
Initialize Slack Space: Overwrites slack space (the unused bytes in the respective last clusters of all cluster chains, beyond the actual end of a file) with zero bytes. This may be used in addition to "Initialize Free Space" to securely wipe confidential data on a drive or to minimize the space a compressed disk backup (like a WinHex backup) requires. Close any running or resident program that may write to the disk prior to using this command. Available in WinHex only, not in X-Ways Forensics.
Initialize MFT Records: On NTFS volumes, WinHex can clear all currently unused $MFT (Master File Table) FILE records, which may contain metadata (e.g. names) and even contents of previously existing files. Available in WinHex only, not in X-Ways Forensics.
Initialize Directory Entries: On FAT volumes, WinHex can clear all currently unused directory entries, to thoroughly remove traces of previously existing files or earlier names/locations of existing files from the file system. Useful especially in conjunction with the function to initialize all free space. Available in WinHex only, not in X-Ways Forensics.