It is frustrating that configuration files ending in .cfg, .pcf and .ucf do not preview in Windows Explorer (File Explorer from Windows 8 onwards). There is a simple solution.
Paste this text into a new text document:
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.cfg]@="MicroStation Configuration""PerceivedType"="text""Content Type"="text/plain"
[HKEY_CLASSES_ROOT\.pcf]@="MicroStation Project Configuration""PerceivedType"="text""Content Type"="text/plain"
[HKEY_CLASSES_ROOT\.ucf]@="MicroStation User Configuration""PerceivedType"="text""Content Type"="text/plain"
Rename the document Mstn_cfg_WindowsExplorerPreview.reg (be sure to have read Windows - Make sure File Extensions Are Visible! first otherwise you might end up with Mstn_cfg_WindowsExplorerPreview.reg.txt which will just open as a text document!).
Double-click the renamed file to enter the values into the registry.
.cfg, .pcf and .ucf files will then preview as text files.
This does not conflict with file association, I recommend associating .cfg files with Notepad++. As mentioned in Making Configuration Files Legible in Notepad++ this is a very capable text editor.
This article describes how to make changes to the Windows Registry. For information about how to edit the registry, view the Changing Keys And Values online Help topic in Registry Editor (Regedit.exe). Note that it is recommended that you should make a backup copy of the registry files (System.dat and User.dat) before you edit the registry. Use Registry Editor at your own risk.