XP, 2003, 2007? Might make a difference. In fact, I think the version of Office might be more important than the version of the OS (XP, Vista).
While writing in Irish (Gaelic) I need to be able to accent all vowels, both upper and lower case. In XP I set up short cuts as follows: ctrl+vowel gave me the lower case accented vowel, while alt+shift+vowel gave me the upper case vowel. Now in Vista the previous set of short cuts works fine in Word, but in Outlook alt+shift+o sends me to Format. I need to disable this function in Vista Outlook. Please do not suggest that I use the number pad to get upper case accented "o".