HELP HELP HELP

I want to change the image that is used for the logo. I have disabled the logo on my store site. I'm not sure if this is where the image in being pulled from but I just can't figure it out.

Currently I can't see any logo, not even the Zen Cart logo that I've seen other posts about.

Where do I start. I've spent the past several hours looking through the various php files but I must be missing it.