A hard drive failure occurs when a computer's hard drive stops functioning properly, leading to data loss or inaccessibility. This can happen due to various reasons, such as mechanical issues, electrical failures, or software corruption. When a hard drive fails, users may experience slow performance, unusual noises, or error messages. Preventing hard drive failure involves regular maintenance, such as backing up data and monitoring the drive's health. Tools like SMART (Self-Monitoring, Analysis, and Reporting Technology) can help detect potential issues early. If a hard drive fails, professional data recovery services may be needed to retrieve lost information.