I think you're having the same problem we had with our lab PCs a while back. This led to an embarrasing situation, where a very famous and elderly scientist visited us, tried to use a computer, and wound up with naked women all over the screen. As I recall, AdAware doesn't work for this, you have to clean out your registries. What is the name of the homepage you have? If it's the same one we had, I can tell you what to do.