In ArcMap, a geoprocessing tool fails with Error 00210 when creating an output to a personal geodatabase.
The problem occurs due to a geoprocessing tool running in the background with the 64-bit Background Geoprocessing product installed, which replaces the standard 32-bit background geoprocessing in ArcGIS Desktop. Personal geodatabases are not supported in 64-bit environments, and ArcMap is a 32-bit application that communicates with a database through 32-bit client libraries. The 64-bit background geoprocessing requires 64-bit client libraries to make a connection.
Note: It is advisable to migrate from a personal geodatabase to a file geodatabase as file geodatabases support 64-bit environments. For more information on creating a file geodatabase, see: Create a file geodatabase.