In Windows Explorer the preview pane is something I normally turn off to give me more screen space. There are times though when it can be really handy. For example when browsing through a large number of text files or images rather than opening each one individually.
So what do you do when you have an unusual file extension that doesn’t work with the preview pane?
A program I use creates a queue of files with an extension of “.cnm”. They are plain text files, but when you try to see them in the preview pane, you just get the “No Preview Available” message. This has actually bugged me for YEARS but for some reason I just kept finding other ways to deal with it.
So I had a moment today where I had hundreds of these files I want to flick through and I finally decided to figure this out once and for all.
The first thing is to get it associated with a program that you know works with preview for the type of file this is. In this case we want Windows to consider a CNM file the same as a text file, so I’m going to set it up the same as a TXT extension
1. Open the file. Because Windows doesn’t recognise what type of file it is, it will ask what you want to open it with. Choose “Select a program from a list of installed programs”
2. Select Notepad (or whichever program is appropriate), and leave the “Always use the selected program…” box ticked
3. Open REGEDIT and browse to “Computer\HKEY_CLASSES_ROOT\[extension]”
(steps updated from suggestion by “Guest”)
4. On the right-hand pane, right-click and select new string value
5. Name the new key “PerceivedType” and set the value to “text”
6. Now go and check your file and the preview pane should now work to display the contents