Recovery Translator v.4 is an application that will allow you to change the language of the recovery menu on firmware 3.71 M33. The application is made to work on PSP Fat or Slim. Remember that this software manipulates files in the flash, so, use with caution & under your responsibility.

http://forums.qj.net/f-psp-development-forum-11/t-recovery-translator-v4-release-132364.html