How do I make Zoom Player my Default Player?

Open the Options Dialog, go to the File Association page. You will see a list of file extensions, each extension represents a file format. The most popular media formats are AVI, MPG and WMV, but you can pick any extension on the list and then press on the "Apply" button to Associate Zoom Player with these file types.

Once associated, the selected file types launched from within Explorer or any other file manager will then call upon Zoom Player to play the file.