Create a locale.ini and save it in the UEFA EURO 2004 main folder and put this inside:
[OPTIONS]
TEXT_LANGUAGE = eng
INSTALL_LANGUAGE= eng
[]
AVAILABLE_LANGS = ger,eng,spa,dut,fre,ita,jpn,kor,pol,por,swe
(If you don't know how to make a locale.ini file, then you just open a text-program (for example Notebook) and put the lines in there and when you save the file and make sure you name it locale.ini)
And when you have saved it in the UEFA EURO 2004 Main folder you can start playing again. I think this should help, if not; I have no clue.
This is for FIFA, but I think it will work for EURO too.