Do this to change the cell font style to what you want.
(Note: I'm guessing you have Word 2007 or 2010)
1.Click in a cell you want to change.
2.Click the Home tab on the Ribbon.
3.Click the arrow in the lower right corner of the Styles section.
4.The style for your paragraph (probably Table Cell) should have a bold box around it. You may have to scroll down to find it.
5.Hover the cursor over the style. A listbox arrow should appear. Click it.
6.Select Modify from the list box.
7.Click the Format button and select Font.
8.Make the changes you want.
9.Click OK.
10.If you want this to carry forward to other documents based on the template this one is based on, click the radio button for New Documents Based On This Template.
11.OK out of everything.
All paragraphs in the document with that style should adjust themselves.
When you close your document, you may see a warning message asking if you want to save the changes to Normal.dotx. This is an anti-virus measure, intended to alert you that something has changed in Normal.dotx. In this case, you made the change, so you want to accept it.
That should do it.