What utility would you use to check for and fix file system errors on a hard drive?

To check for and fix file system errors on a hard drive, the Check Disk utility is the appropriate choice. This tool, commonly known as CHKDSK, scans the file system and file system metadata of a volume for logical and physical errors. If any issues are found, it can repair them, ensuring the integrity of the file system.

Disk Cleanup is designed for removing unnecessary files to free up disk space, such as temporary files and system files, but it does not address file system errors. Task Manager is a system utility that provides information about running processes and resource usage, allowing users to manage applications but not to repair any disk errors. Disk Defragmenter optimizes the file system by rearranging fragmented data to improve access speed, but it does not check for nor correct file system errors.

Therefore, using Check Disk is essential for maintaining the health of the hard drive's file system, making it the suitable option for this task.