A PC tune-up utility is an application that digs deep into your computer and fixes trouble areas. It performs several functions, including defragmenting your PC's hard drive, repairing the incredibly problematic Windows Registry, and freeing up disk space by deleting useless and duplicate files. Some tune-up utilities perform just those basic functions, while more elaborate ones add numerous features that improve your computer in interesting ways. For example, Iolo System Mechanic cleans gunked-up PCs with its real-time system monitoring; Ashampoo offers a file-deletion tool and backup app; and AVG offers a driver updater. We tested all the tune-up utilities in this story on a junked-up Windows 10 test bed. Note that Microsoft's operating system has many built-in tools for improving your PC's performance, though they're scattered throughout the OS (unlike the third-party tune-up utilities mentioned here). Please note that while tune-up utilities were valuable tools in the Windows 8/7/XP eras, we now find them harder to recommend in the Windows 10 era, as the operating system lets you effectively tune-up your PC for free.