Now, about the loading of modules - you do not have to enable an extention if you're not planning to use it.
To disable a module, open your php.ini and put the # sign in front of each extention.
The most common extentions you should enable by not putting the # sign in front are mysql(if you are using a mysql database) and gd2 - this is a handy extention for manipulation of pictures and image files.
If you're not using the rest of the extentions, just disable them.
Then, after editing and saving the php.ini file, restart the apache server. Then create a new php document, e.g. test.php, and put it in the apache document_root directory. In the test.php file put only this statement:
<?php phpinfo(); ?>
By typing in your browser
http://localhost/test.php you should see a very nice table with infromation about your php installation.
Check and advise what is the outcome. If everything is ok, you should see the nice table with a lot of info. If php is not working, then you should see the php code in your browser window.
Cheers.