if your pc opens the $$a file, but it's the wrong application, you'll need to change your windows registry file association settings. in other words, windows is associating $$a file extensions with the wrong software program.

How would the previous sentence be correctly capitalized?
If your PC opens the $$A file, but it's the wrong application, you'll need to change your Windows registry file association settings. In other words, Windows is associating $$A file extensions with the wrong software program.