Magento: Admin Controller Override

I had to override adminhtml controller class (Mage_Adminhtml_System_ConfigController) with my module’s controller class (MyNamespace_MyModule_ConfigController).
It was really tough to find the right solution. I googled, searched in magentocommerce forum and found a lot of solutions. But they didn’t work for me.

After searching & trying more, I got some work done with the following piece of code:-

<global>     <routers>         <adminhtml>            <rewrite>                <system_config>                    <to>MyNamespace_MyModule/config</to>                    <override_actions>true</override_actions>                    <actions>                        <save>                            <to>MyNamespace_MyModule/config/save</to>                        </save>                        <index>                            <to>MyNamespace_MyModule/config/index</to>                        </index>                    </actions>                </system_config>            </rewrite>        </adminhtml>     </routers> </global>

But this gave “404 Error Page not found” when I go to System->Configuration.
Finally, I did the controller override with the following code:-

<global>     <rewrite>         <mynamespace_mymodule_config>             <from><![CDATA[#^/admin/system_config/#]]></from>             <to>/mymodule/config/</to>         </mynamespace_mymodule_config>     </rewrite> </global>