Does ArcGIS 9.0 need to be completely uninstalled before installing ArcGIS 9.1?
Last Published: April 25, 2020
Answer
Yes. Everything related to ArcGIS 9.0 (ArcGIS Desktop, ArcInfo Workstation, Desktop Developer Kit, Tutorial Data, Python, Crystal Reports and any third-party customizations, toolbars, etc.) must be uninstalled before installing ArcGIS 9.1.