If you hold down the Shift key while selecting the Format menu item you can change the appearance of the _screen font. All the other windows can be right clicked and select Font from the menu.
While VFP is not running you could also use regedit and go to the HKEY_CURRENT_USER\Software\Microsoft\VisualFoxPro\6.0\Options and HKEY_CURRENT_USER\Software\Microsoft\VisualFoxPro\6.0\Desktop keys and alter the fonts there. You should be careful if you do it in the registry directly.
>How I can change fonts arial with other in general environment/VFP6.0/