if your pc opens the w3d file, but it's the wrong application, you'll need to change your windows registry file association settings. in other words, windows is associating w3d file extensions with the wrong software program.

Write the above sentence using proper case.
If your PC opens the W3D file, but it's the wrong application, you'll need to change your Windows registry file association settings. In other words, Windows is associating W3D file extensions with the wrong software program.