Windows 7 has lost the ability to easily modify the file assocation actions. I recall it being moderatly simple to modify the 'edit action' in XP.
The problem we have now is that TRIM (184.108.40.2060 - and will be for a few more months yet) uses the 'edit' action to send files to their applications. Windows7 appears to treat CSV files as Txt, thus sending them to notepad. So when a user trys to edit a TRIM registered CSV file, it opens in notepad rather than Excel.
I have managed to modify the registry to change this behaviour, so CSV files are edited by excel, but it has flow on affects. If I make this change, then all txt files are then opened in Excel! This may be a suitable solution for many users but not all.
You can still associate file extensions with programs in Windows 7 without touching the registry.
Right click on a file and choose "Open With" (if there is already an association) or "Open" (if not - and "Open With" does not appear).
Choose the program you want to open the file with (bear in mind the somewhat "concealed" option to expand the list of other programs (The little down arrow on the right of the line) - or the browse button.
Don't forget to check the "Always Use the selected program....." tick-box and press OK. All future "opening" of files of this type - including from TRIM will use the selected program.
At least it does on my systems and I don't think there is any general IT policy associated with this.
Note: Any posts I make on this forum are my own personal opinion and do not constitute a formal commitment on behalf of Hewlett Packard Enterprise.