Get an anti-virus program immediately!
I would be amazed if you are not already infected running on the internet without a resident av program!Antivirus programs - freeware
(you can only use one resident anti-virus program on your computer. More than one will conflict)
Avast Anti-virus freewarehttp://www.komando.com/bestshareware.asp
I would also recommend that you run the Windows Live Onecare Free Scan
(You must use Internet Explorer for this to work)
It will say "Get a free PC safety scan"http://safety.live.com/site/en-us/default.htm
Make sure you click "Full Service Scan"
in the middle of the page and not the "Try It Now Free" on the right side.
Allow it to download an Active X component.
Choose "Complete Scan" in the window that opens
Do not click on anything else that offers you a free trial or to sign up if you live in the US.
Allow it to scan - it may take quite a while, maybe two hours or so depending on how big your hard drive is and how fragmented your registry and drive are.