How to Associate a File Type or Protocol Default Program in Window 7

I was trying to associate (or map) a particular file extention to open with a particular application, and was having a nightmare of a time getting this to work.

There are two common methods to do this.

Option 1: Right click on the file and select 'Open With':

Option 2: Open control panel and click on Default Programs:

then click on 'Associate a file type or protocol with a program':

No matter which method I chose to use, the file just would not map to the application I was trying to associate it with.

Suddenly, I had an epiphany when, I realized that the program (application) I was selecting as the default application for the file type, had a space in the application name. i.e. In my experience, you may have these issues if you have spaces in your application's program name:

for example:
'My_Application_V3.exe' is OK.
'My-Application-V3.exe' is OK.
'MyApplicationV3.exe' is OK.

'My Application V3.exe' is NOT OK!


You must remove the spaces from the program name or at least replace spaces with underscores or hyphens, otherwise like me you'll likely find you have trouble getting any file types to associate with the application!