When editing a personal geodatabase and deleting features or when feature classes and tables are deleted from a personal geodatabase using ArcCatalog, the size of the MDB file may not change.
Personal geodatabases are stored and managed in Microsoft Access data files (MDB files). As data is added and edited within a personal geodatabase, the MDB file increases in size to accommodate the data and may become fragmented on a disk. The MDB file does not decrease in size when data is removed; space allotted for the data continues to be held in reserve by the MDB file.
Use the Compact Database command in ArcCatalog to compact the personal geodatabase. Compact rearranges how a fragmented personal geodatabase is stored on disk. Compacting a personal geodatabase often reduces its size and improves performance.
See the following ArcGIS Desktop help topic for more information on compacting a personal geodatabase:
Compacting a personal geodatabase.