How to completely disable Magento extension

Sometimes you may need to temporarily disable a Magento extension or module so it cannot affect the store. Disabling module output in the Backend does not disable the extension itself and does not free its memory or CPU usage.

Warning: Do not use System > Configuration > Advanced > Disable Module Output as a substitute for disabling the module.

You can disable an extension by editing its XML configuration file and then flushing the Magento cache.

Open app/etc/modules/ under the Magento root in File Manager.
Open the module configuration file. It consists of the developer name and extension name with an .xml suffix, such as EM_Themeframework.xml or Mage_Log.xml.
Change the <active> value from true to false:

<config>
    <modules>
        <EM_Themeframework>
-            <active>true</active>
+            <active>false</active>
            <codePool>local</codePool>
        </EM_Themeframework>
    </modules>
</config>

Flush the Magento cache.