I'm not sure, but I think the change was using the font "Segoe UI" instead of "Tahoma", and maybe, Lucida Grande.
I haven't tried it, but I assume you can edit the fonts, which are specified in (basically) a text file (at least, for iTunes 10).
Make a backup of the file before you edit anything (or you can repair/reinstall if you mess it up). See the following post for some more info:
http://discussions.apple.com/message.jspa?messageID=12226047#12226047
You'll want to edit the "font", not the "xp-font". I can't tell you what fonts will work.