I just downloaded a copy of a production website made in Drupal and threw it into my WAMP installation. Now, whenever I try to access it through the browser, I get the following message (on an "Opening" pop-up window generated by Windows XP):

You have chosen to open

which is a: application/x-httpd-php
from: http://localhost

What should Firefox do with this file?
() Open with [BROWSE]
() Save File

The ironic thing is that my other installs of Drupal on my localhost work flawlessly, even with HTACCESS files in their respective directories. I've tried removing these anyway just to see if they were causing any problems, and not surprisingly, it did nothing to help this. Even a "test.php" file with nothing more than an echo statement in said directory seems to have problems... This only happens to this directory and it's driving me nuts! I just have no clue what's causing it because this has never happened before like this... Every other directory, file, etc. in other directories seem to work perfect. I just don't get it.

Do any of you have any ideas about what's causing this?