changing image

Hi,

I've got an image (logo) I want to change on my site. The logo is displayed on every page, but I'm affraid that I don't know how to replace the image file with a new one.
I've tried to rename the file (it's a PNG) to the new file's name (it's a JPG), but then the image isn't displayed (error).
The problem is that I can change it page per page, but that'd be half a day's work.

Does anyone know how to do it in a quicker way?

creating a new image and calling it exactly the same as the current one. Hey presto. Changed on all pages.

Be sure its the same EXACT size tho. Also put it in the same directory (basically Overwrite the old one!)

It wouldn't take more than a few minutes to change the documents even if you have 100. Find & Replace is pretty handy. ;)