Photoshop: Cann't get it to open .JPG extension from file.

When I double click on a .JPG file it will not open by Photoshop. It wants to use viewer.exe. I went as far as trashing viewer.exe. I have tried to change the View-->Folder-->options-->File Type. and I get a message: The extension '.JPG' is already in use by file type 'ViewerFrameClass'. Choose another extension. I also cannot find in the file types ViewerFrameClass. I have Photoshop version 4.0. HELP! I have tried everything I can think of!

I think you must do like this.. you just click right key on your file then click on "OpenWith" to chose your extension.