Configuring Yahoo Messenger 7
In the main yahoo messenger window, hit control+shift+P for 
the preferences.
Then tab or shift tab to the tree view of setting categories,
In the tree view, arrow up or down to appearance.
Then tab to a check box, use colors and
fonts from others, and make sure that is unchecked.
Tab to the skins button and hit spacebar.
Tab to the skins combo box and choose classic.
Tab to the font button and hit spacebar.
For the font choose Arial.
Then enter on okay to save your changes.