How to remove file association?

Just select/highight (single click) one of the .dat files. Do a GetInfo CMD-I or File>GetInfo (or just use "More Info...") Click on the disclosure triangle next to "Open with," select the App in the dropdown menu you want to as the default and hit the Change all button. Other than that, when you want to open a .dat, don't double click on it or do File>Open, instead highlight it and go to File>Open with.

EDIT Or do the control click as Dave Sawyer suggets.

I don't know of any way to remove the association permanently. But you can change what application a given file type is associated with. Click on a representative file, Get Info (Command-I or under the File menu), go to the Open With.. section, select the appropriate application to open the files, and click the Change All button.

Alternatively, just right-click (or control-click) on a file and you can select what application to open the file with.

Regards.

In addition to the other advice, you could set the default application for .DAT files to an application that cannot open files. For instance, you could, using the Get Info window on a .DAT file, change the default application to Finder (/System/Library/CoreServices/Finder). Then, when you double-click on the file, nothing will happen.

There is a free preference pane, RCDefaultApp, that will allow you to disable the file extension association. It is available here: <http://www.rubicode.com/Software/RCDefaultApp/>.

If you keep the applications that you need to use to open .DAT files on the Dock, then you can drag the files to the appropriate Dock icon to open them.

bd

If RCDefaultApp does not behave the way you expect, perhaps you can contact the developer of the program. I think "disable" effectively does what I expect, but I do not know where these associations are stored.

bd