edit: I just looked at this thread again. I didn't fully scroll down and see that you already said it was Windows.
Ubuntu/Mac OS X both have distinctively different ways of font rendering. Windows' font rendering looks more readable (in my opinion), and OS X/Ubuntu's were designed for print.
I hastily put this together to better illustrate what I mean.
edit: I just looked at this thread again. I didn't fully scroll down and see that you already said it was Windows.
Ubuntu/Mac OS X both have distinctively different ways of font rendering. Windows' font rendering looks more readable (in my opinion), and OS X/Ubuntu's were designed for print.
I hastily put this together to better illustrate what I mean.
http://i.imgur.com/Ag5DK.png