Instructions
Download CWCheat. Without this program, you cannot change the name of your character. See References for the download link.
Insert "Monster Hunter Freedom 2" into the PSP and select it in the "Game" category from the PSP's main menu.
Hold "Select" a couple of seconds to open CWCheat.
Choose "Cheat searcher," then "Memory editor" in CWCheat.
Find your character's name on the right panel. Press "X" on the first letter of your name. Type in your new name. Press "X" when you are finished typing in your new name. Press the "circle" button a few times to exit CWCheat and to go back into "Monster Hunter Freedom 2."
Save your "Monster Hunter Freedom 2" game so that your new name will be saved.