The CleanShapefile.exe utility was installed with the ArcObjects Developer Kit at ArcGIS version 8.x. The utility looped through shapefile features and created a new shapefile containing simple geometry.
The CleanShapefile utility is no longer installed with the ArcObjects Developer Kit.
CleanShapefile has been replaced with the Repair Geometry tool available in ArcToolbox. Repair Geomtery is available to all ArcGIS license levels and can be used with both shapefile and geodatabase feature classes.
ArcToolbox also contains a Check Geometry tool that creates a DBF or geodatabase table that lists all non-simple features found in a feature class. This tool only reports the features with non-simple geometry; it does not repair them. The Check Geometry tool is found under Data Management Tools > Features > Check Geometry.