When a partition is deleted, in general, only its partition table entry is removed from a table; and although the data is no longer accessible, some still remains on the disk until being overwritten. Specialized recovery utilities, (such as TestDisk and gpart), can locate lost file systems and recreate a partition table which includes entries for these recovered file systems. However, some disk utilities may also overwrite a number of beginning sectors of a partition they delete. For example, if Windows Disk Management (Windows 2000/XP, etc.) is used to delete a partition, it will overwrite the first sector (relative sector 0) of the partition before removing it. It may be possible to restore a FAT32 or NTFS partition if a backup boot sector is available.
Hard disks can be compressed to create additional space. In DOS and early Microsoft Windows, programs such as Stacker (DR-DOS except 6), SuperStor (DR-DOS 6), DoubleSpace, or DriveSpace (Windows 95) were used. This compression was done by creating a very large file on the partition, then storing the disk's data in this file. At startup, device drivers opened this file and assigned it a separate letter. Frequently, to avoid confusion, the original partition and the compressed drive had their letters swapped, so that the compressed disk is C:, and the uncompressed area (often containing system files) is given a higher name. (SuperStor required a separate device driver to be loaded, DEVSWAP.COM).
Versions of Windows using the NT kernel, including the most recent versions, XP and Vista, contain intrinsic disk compression capability. The use of separate disk compression utilities has declined sharply.
Disk partitioning is the act of dividing a hard disk drive into multiple logical storage units referred to as partitions, to treat one physical disk drive as if it were multiple disks. Partitions are also termed "slices" for operating systems based on BSD, Solaris or GNU Hurd. A partition editor software program can be used to create, resize, delete, and manipulate these partitions on the hard disk.
