In update 17.2 to open a V7 DGN file you will have to set a preference to be able to open it as read-only or upgrade it to the V8 file format. The Allow V7 DGN File Open check box is now added to the Preferences dialog, Operations category for this purpose. You must turn on this setting before opening a V7 DGN.
If you try to open a V7 file without enabling this setting you will be alerted by a message.
Once you have turned on Allow V7 DGN File Open in the preferences, you will see the following message while opening a V7 file:
Here you can choose to upgrade to V8 file format or open the file as V7 read-only.
To find out what else is new in this update please watch New in MicroStation Update 17.2.