Having Trouble changing only the "Add to Cart' button...

Hi everyone. I am trying to figure out how to change the add to cart button to a custom one I made.

I've searched the forums, read up on the tutorials (https://www.zen-cart.com/tutorials/index.php?article=51) , and I know how to change buttons. In fact, I have already changed the BACK TO SHOPPING button and et cetera.

The problem is, I am unable to change what seems to me ONLY THE "Add to Cart" button and I need to be able to change it.

Anybody with the same or similar problem? I've been trying for hours to find a solution to this problem but without any luck at all. I hope somebody can help.

thanks..

UPDATE:
So, because I ran out of things to try in order to fix my problem. I went ahead and deleted the add this to cart button out of the core default template in

/shop/includes/templates/template_default/buttons/english

to see what would happen.

The result,,, nothinig changed. I don't have the button_in_cart.gif in none of my folders

/includes/templates/CUSTOM/buttons/english
or
/includes/templates/template_default/buttons/english

what is going on/!??!

any help. anyone please??

Please do not repost the same problem in multiple places.