Download the AVS file and navigate to the file in File Explorer
Righit click the file and click on "Properties"
Next to "Opens with:" click "Change"
Scroll to the bottom and choose "Choose an app on your PC"
Copy this path and paste it into the window next to "File name:"
c:\Program Files (x86)\Seon\vMax3\vMax3\vMaxView.exe
Click "Set Default" and that will make the file open with the proper program