Hi,
Right-click on a blank area on the desktop, then goto Properties. You
should then be in Display Properties. Click on the 'Settings' tab, then
click 'Advanced'. On the general tab, you can change the DPI setting to
whatever you want and it will then scale all fonts according to what you
enter. You'll want to click on the 'Custom' setting and then you can drag a
ruler and visually see how big the font(s) will look.
Matt