I cannot do a simple UNION function using the shapefiles, into either a new shapefile or into a personal geodatabase
I believe the error is occurring as the output path has the file extension for a shapefile (.shp) in a database.
is not valid as it is attempting to create a shapefile in the database
would be as it creates a shapefile in a folder.
would be as it creates a feature class in a file geodatabase.
This lines up with the two output paths visible in the screenshot.
I'd also generally recommend using feature classes in a file geodatabase over shapefiles or personal geodatabases. If we need to export to shapefile for say importing into another software, we can always do so when required.
Retrieving data ...