Final answer:
Paint is the utility tool a support agent would least expect to use for operating system issues, as it's a graphic editor, unlike Disk Cleanup, System Restore, and Task Manager, which are used for system maintenance and troubleshooting.
Step-by-step explanation:
Among the utility tools listed, Paint is the tool you would least expect a support agent to find useful when solving problems with operating systems. The other tools mentioned are all directly related to system maintenance and troubleshooting. Disk Cleanup is used to remove unnecessary files to free up space on a hard drive. System Restore can revert system files and settings to an earlier point in time, which can resolve issues caused by recent changes to the system. Task Manager is essential for monitoring and managing system processes and applications. Paint, on the other hand, is a graphic editor and is not typically used to diagnose or repair system issues.