I doubt very much that it saves it in Open Office format. Much more likely is that you've got Open Office set as the defualt for opening Word documents, so once you've saved it, if you double-click it will open if OE instead of Word.
All you need to do is right-click a document that you've saved, choose "Open with" then "Choose default program" and select Word. After that, Word docs will always open in Word.
But if you hate Open Office with a passion, why don't you just uninstall it?