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BitLocker is a full-disk encryption feature included with Windows Vista and later. It is designed to protect data by providing encryption for entire volumes. By encrypting the hard drive, BitLocker prevents unauthorized access to the data stored on the drive, securing it in case the laptop is lost or stolen. BitLocker is preferable over options like Windows Backup (which is for data recovery, not encryption), Shadow Copy (used for backup and does not encrypt data), and Trusted Platform Module (TPM, which is a hardware component used alongside BitLocker for securing encryption keys).