How Can I Stop Dreamweaver from Opening .JS Files?

I believe that is a Java Script file extension. Not knowing what program you want to open them, I would right click the file, then click "Open With" and brows to to program that you want to open them. Make sure the the little box that says "Always use this program to open this type of file" is clicked and then click ok. Each version of Windows does this a little differently, but just use your head a bit and you'll get it set right.