It's hard to tell what's going on from your description and without actually being able to see the PC. If I had to guess I would say it sounds like your browser has been hijacked to me. You can probably clean it up. Do you have anti-virus and firewall software? Ad-aware is also somewhat useful for hijacks. After you clean it up you should switch to Firefox or better yet a Linux distro and Firefox. I had to slip in at least one Linux fanboy comment. It's so hard to hold them back!