1. Calm down. The fact you are posting means you are online and limping along.
2. Ignore the jokers who are telling you to reformat, install Linux (geeks)
3. If you are Windows based -- go to www.Norton.com (my favorite) or mcafee.com -- both have some freeware, but it is easier and chaper in the longrun to just buy their packages. Norton Antivirus is the best I have seen.
Pay the 50 bucks, download the scan, run it, you'll be OK.
Good advise, but Norton most likely won't solve this problem. Sounds like a good ol' IE adware based browser hijacking.