Bug: 'Examine all file extensions' option does not enable Microstation files with non DGN extensions to be listed
Microstation files can be created with file extensions other than DGN. These files can be recognized by ArcGIS by checking on an ArcCatalog option found under Tools > Options > CAD tab > Examine all file extensions.
At version 9.0, checking on this option does not allow the files to be listed.
This is a known issue.
Place a recognized CAD format file with a standard DWG, DXF or DGN extension in the same folder as the other Microstation files. Refreshing the directory now lists the additional Microstation files.