Sounds like you picked up a virus. I work at a college full time a school district part time in the IT Dept. First question, Do you have an up-to-date antivirus program? I mean something that you either pay annually for updated virus definitons or free down loads? If you do, time to run a scan. If not, there is a really good one out there and it's free, it's called AVG Free. Google it, and just make sure that it's free (some sites charge), and down load it and run it. Also, you can download for free "Adaware", it gets rid of spyware, adware, grayware and a variety of other garbage that slows down your pc. Tell me how this works for you, if your still having a problem, let me know and I will tell you something else to try.
Doug