There’s a lot of registry cleaner software out there, and many of it come with adware or spyware right away, or promise major system speedups. The System Repair module allows you some basic cleanup and repair without the need to risk installing a dedicated registry cleaner.
System Repair processes only a handful of categories where changes might positively affect user experience, like helping Windows find misplaced help files. It can either delete or repair broken entries, with the repair offering you to locate or search for moved files, for example.
In general, we recommend not to use registry cleaners, optimizers or defragmentation utilities at all.