Jmann

Recently my internet hasn't been loading pages properly. In Firefox, it scrunching words together, and leaves links blank. For example, on yahoo it doesn't show the links for news and on the sides it scrunches up words or just has one letter to represent them. When I'll type in the search box it doesn't show what I'm typing; the search assist will work but won't show what I am typing. For internet explorer, it says there is a problem displaying yahoo and it must go to compatibility mode. I have no idea what is causing this. Could not being able to install windows vista service pack 2 have an effect on it? Or is it cookies, or internet settings, or a virus, or something else along those lines?
Please, please, I need some help because i have no idea what to do here.