Well, a last time now.
YOU DONT NEED IT EXTERNAL!!
If you got the latest Hermes 4B and also a BM with Peek/Poke like OM 2.1 you just have to copy it over to your external once, then open up you BM and copy to internal with (o button). Make sure you edit and replace the Param.sfo in the MOH Folder i.e. BLUS30436/PSGAME.
So now hit "L1" and activate the mem patch, now run the game through xmb disc symbol. Install the patch 1.01 online or get it offline and install as PKG (make sure its the correct region!).
Let the game data install and have a lot of fun playing MOH. No need to install gamedata over and over,,,senseless!
So now read my instruction carefully, it will work 100%, its at least 20 times confirmed. Be patient and follow each step correct.
A little hint... If you get the param.sfo from the wild make sure the one you et it from is real, or just give it a try and edit yourself, not that hard. Get SFO editor and change the String Firmware 3.42 to 3.41 and save, thats it.