If you’ve had the pleasure of upgrading to 10.5, you may have noticed that OS X suddenly began acting like Windows. Whenever you download a file, it now prompts you with a message, asking if you really actually want to open the file. What possessed the fevered brains of the development team is beyond my comprehension. Well, yes, thank you, I downloaded the file for a pretty effing good reason and I’m rather sure that I want to open the file that I, myself, downloaded. I wasn’t just saving it for a special occasion.
Now, you can’t disable this “feature” altogether. You may have seen the fix which enables a custom folder action for the Download folder, but this is a stopgap measure at best. As you may have discovered, as soon as you expand a zip or other compressed archive, it will prompt you upon opening each and every file contained within.
I recently found a post which describes how to disable the prompt, but only on a file-type basis. Still, this is a great improvement, assuming you have the patience to insert your most commonly used filetypes. (Note to self: at some point, post a comprehensive version of this file.)