okay...first off you should probably make a quick backup of all of that in case something goes wrong..
If you click your mouse somewhere in the text of that file, and then click ctrl A with your keyboard, it should highlight everything.
if everything is hightlighted, click ctrl C to copy all of that, then open a text-editor (in Windows I think it is called notepad) and paste all of that content into text-editor, then save that to your desktop. This is just in case..you can delete after you are done...
Once you have your backup made, let me know