Do you mean your computer is slow when you're using the internet ie when you're using your browser (Internet Explorer/Firefox)? Just wondering as you say it takes ages for pictures to come up which sounds like you mean when you're surfing
If so, it could be a problem with your ISP or it could be something simple like you need to empty your temporary internet files folder. If you use IE7, go to Tools, then Internet Options, then Browsing History, then you can delete your temporary internet files. Worth a try anyway