From Word 2003's Help:
On the Tools menu, click AutoCorrect Options.
To select the options, do one or more of the following:
To show or hide the AutoCorrect Options buttons, select or clear the Show
AutoCorrect Options buttons check box.
To set the capitalization options, select or clear the next five check boxes
in the dialog box.
To turn on or off the AutoCorrect entries, select or clear the Replace text
as you type check box.
To turn on or off the spelling checker corrections, select the Replace text
as you type check box, and then select or clear the Automatically use
suggestions from the spelling checker check box.
Note: To select the Automatically use suggestions from the spelling checker
check box, you must first turn on automatic spell checking (On the Tools
menu, click Options, and on the Spelling & Grammar tab, select the Check
spelling as you type check box