How can I change the product thumbnail display in Magento?

I am trying to change the product thumbnails in Magento. I am looking at this line in /app/design/frontend/default/THEME/layout/catalog.xml:

<block type="catalog/product_view_media" name="product.info.media" as="media" template="catalog/product/view/media.phtml"/>

This would lead me to believe that I can change the file /app/design/frontend/default/THEME/template/catalog/product/view/media.phtml. However, when I make changes to this file, nothing changes. Even blanking the file doesn't cause any changes. I have the cache completely开发者_开发技巧 disabled, so that can't be the problem.

If I remove the <block... from above, the product thumbnails section disappears completely, so that line must be correct.

What file do I need to edit in order to change the thumbnail display?

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Search the same file in other themes and packeges (depends on what theme is swithced on in the admin panel). Also on of the easiest way is to look in the place you need to change using f. e. firebug and get relatively unique class name or ID and the search it in design folder (grep etc.)