The process for changing the default fonts that Word uses for text in page Headers and Footers is an easy but not too obvious one.
To change the default for any of Word's styles, just follow these steps. The method works for Word 7, 97 and 2000:
1. Select Format-Style.
2. Under List, in the Style dialogue box, select All styles.
3. From the choices offered in the Styles list, choose Header or whatever style you want to alter.
4. Click Modify.
5. In the Modify Style dialogue box, select Add to template, then click the Format button and select Font from the menu that appears.
6. Change the font in the standard Font dialogue box and then click OK in both the Font dialogue box and the Modify Style dialogue box.
7. Repeat steps 3 through 6 for any other styles you want to modify. Click Close in the Style dialogue box to finish the job.