You have been infected with a particularly nasty parasite/spware/malware program that is known for being difficult to uninstal because it repropagates itself.  See the following:

http://www.doxdesk.com/parasite/RapidBlaster.html

I'm not sure if the current spyware removal tools will deal with this one, but you might want to get them and run them anyway, because if you have this parasite, it is likely that you have a lot more.

Spy-Bot Search & Destroy - http://security.kolla.de/

Ad-Aware - http://www.lavasoft.de/index.html

Steve

Note that you are reply to a post that is well over a year old. If you are having a similar problem, and the solution posted over a year ago, with year-old links that may or may not still work, then post a new message and give us the specifics of your particular problem. The types of internet parasites have changed considerably in the last year and your problem may deserve a fresh look. You might also want to post your new message in the General Boards - Virus and Spyware Information and Removal forum.

Steve