Is it just fonts that look out of proportion? Or does everything seem stretched? If everything is out of shape, would be your screen resolution is probably not right for you monitor. Check you resolution in Windows, see that you are using the same in Ubuntu
Not sure how Ubuntu handles font config, I imagine you are using Gnome rather than KDE? You could do from a command line and since it is based on debian, "dpkg-reconfigure fontconfig" (without quotes) as root (I think you use "sudo") will walk you through a few steps for configuring fonts.