Oh, the joys of a bilingual computer.
I've experienced a somewhat similar situation, and have learned to live with it.
My computer came with Windows XP pre-installed, in Spanish. Since I'm currently living in Canada, most of the software I install is in English (I speak both languages, so I quite don't care which language anything is in). My copy of MS Office is in English, and so was the upgrade to IE7. This has resulted in a Frankenstein bilingual operating system, with dialogs such as "Desea continuar? Yes, No, Cancelar" Not only on MS software, but something on some installers seems to mess around with my OS dialogues and make them increasingly bilingual. It used to drive me crazy, but since Spanglish is already becoming my main language at this point, I guess it only fits my situation to have a computer with language identity crisis.