What utility would you use to check disk errors in Windows?

The utility used to check for disk errors in Windows is CHKDSK. This command-line tool is specifically designed to scan the file system and check the integrity of the file system on a volume. When executed, CHKDSK identifies issues such as bad sectors, lost clusters, and directory errors, and it can also attempt to repair these problems, improving the overall health of the disk.

Disk Cleanup is primarily focused on freeing up space on the disk by removing temporary files, system files, and other unnecessary items to optimize storage. While it helps maintain the drive's performance, it does not check or repair disk errors.

Defragment and Optimize Drives is used to rearrange fragmented data on the disk to improve read and write efficiency. It does not check for disk errors and therefore is not appropriate for verifying the disk's integrity.

System File Checker is another tool that focuses on the integrity of system files, scanning and repairing corrupted or missing system files but not addressing issues specifically associated with the disk itself.

Thus, CHKDSK is the correct choice for checking disk errors, as it directly addresses the structural quality and integrity of the disk drives in Windows.