Language problem

Hello i have bought a week ago my new pc system. I have installed the english Vista Ultimate pack. when i download a file with the extension Srt. used for subtitles in movies my pc couldn't recognize the greek language. Anyway i can write in greek. When i found about that i downloaded the Greek language pack from the vista updater. The download was installed succesfully and after that another update was availiable about the greek package. Both were succesfully installed but my system still won't read greek. I dont want to change my whole system from english to Greek. I only want my pc to be able reading greek. Thank you for your help.