In a Windows XP environment DGN files with names containing space characters can not be opened by double click from Windows Explorer .
Open Windows Explorer.
Go to ‘Tools’, ‘Folder Options’.
Go to 'File Types' and scroll in the list to dgn.
Activate 'New'. Type dgn as file extension and click 'ok'.
Scroll in the list to dgn and activate 'advanced'. (If 'advanced' is not available activate 'restore' first.)
The 'Edit File Type' dialog will open. Activate 'new' action. Type open as the new action.
Activate 'browse' and browse to the desired ustation.exe file.
Edit the path displayed in the 'New Action' dialog. Add "%1" at the end of the path.
The Microstation icon should show now beside the file names in Windows Explorer. The files can be opened by double click.