XP Font Display Question

Ok. So I got XP. I install some software and Bang, my webpage Font Displays are now all messed up.

This is a Snap of Sowpub...



Notice how some fonts are Huge while others are Tiny.

And here's a view of part of the side menu of my website - notice how the fonts are kind of overlapping.



I've uninstalled the software I installed. Nothing.

I uninstalled Firefox and reinstalled it. Nothing.

Any ideas?

Michael Ross