MS office 2004 and the o with a line on the top

I don't think there's a way to type that, but it's easy to get at:

If you're working with Japanese, you should have the "Character Palette" turned on in the Input menu. If you don't, turn it on and marvel at all the neat Japanese features it has--it's basically a simple Kanji dictionary, among other things.

With the character palette open, select "Roman" from the "View" menu. Click Accented Latin in the lefthand box, and find the capital and lowercase ō symbols (not sure if this forum software will properly convert the unicode so that will be visible). Double click on it or drag and drop it into a Word document (or use the "Insert" button at lower right), and bingo, you've got your symbol.

Note that you need to be using a font that contains the character for it to show up right, but you can see which ones do by expanding the "Font Variation" triangle in that window. Also don't forget that you can expand the palette to be as large as you want.

Final note: It's called a "Macron" apparently, so if you type "Macron" in the search box, it'll find all the Macron-ed letters for you.

Final, final note: You can add those characters to the "Favorites" tab up top, and that lets you get at them without sorting through all the accented characters. This is what I did when I was typing a document using Romaji.

Although frankly, these days, I either use double vowels for everything ("Tooru"/"Touru"), or use an umlat (the two dots), since that's much more widely supported in systems that aren't Unicode-savvy. The "hat" works too, and you can type that by just going option-i then the vowel you want the hat on: ô.