From a user viewpoint, the computer is only as good as the data it contains. If the computer can't boot up, it's practically useless. If it can boot up but the files are corrupted and cannot be opened for reading or writing, the file is useless. This happens often enough that data backup and recovery tools are a must with computer users. In fact, it's a good idea to have two copies of important data, just in case the first backup fails. Data recovery tools make sure that the backup is restored and the user can go back to using the computer in as little a downtime as possible. Some data recovery tools have the facility to recover hard disk partition information. As with regular file backup, the recovery tool needs a backup. To recover a hard disk, either a hard disk as a whole is backed up (called a mirror) or just the partition. Commercial data recovery packages such as DriveClone and Ghost can backup a partition or a hard drive and recreate it to repair the failed hard drive, or to write it to another hard disk or computer altogether. These programs can boot from a recovery CD and proceed to do a hard disk and data recovery.
For larger installations, there are data recovery software from vendors like Acronis and Veritas which can backup multi-volume disks and RAIDs using disk backups and tape drives.
Hard disk failure and data corruption is a serious concern. In cases like these when the computer fails to boot up, or the data could not be read, it helps a lot if data recovery tools are ready, in use and allows easy recovery of data.