Chasing, i have a strong feeling what you have is spyware. Hopefully Byteman will post in here as he has a terrific explanation of how to rid your computer of it. In the meantime, i will explain....i am going to do so in two sections: 1. fixing the problem at hand 2. preventing future occurances.
First, you are gonna need a small arsenal of programs, free of course, to take care of this. Listed below are the programs and where to find them:
1. Adaware SE -
www.download.com
2. Spybot: Search & Destroy -
www.download.com
3. Microsoft Anti-spyware Beta -
www.microsoft.com
4. Spyware Blaster -
www.download.com
Adaware, Spybot, and Microsoft are scanning programs that will scan the contents of your computer and look for spyware. Once you download these 3 programs you MUST update the reference definitions. Once you have updated all 3 of the programs definitions, do not scan yet. Spyware Blaster is a passive program that changes and tweaks settings on your system, disables access to know malicious websites, etc. Again, once you have installed Spyware Blaster, make sure you update the definitions and enable all protection.
At this point in time, once all definitions are updated, restart your computer and enter Windows safe mode. You can do this by, once the computer restarts, keep tapping F8 and a menu will prompt you to choose which "version" of Windows you wish to use. Choose safe mode. Once in Safe mode, proceed to scan with Adaware, Spybot, and Microsoft. Once finished, restart and load windows normally.
Next, go online and google free virus scan and use AVG or Trend Micro and scan your computer.
PREVENTION
First of all, ditch Internet Explorer. I highly recommend Mozilla Firefox. Use IE only when its absolutly needed. Secondly, if you are not already, get behind a firewall. There is plently of free firewalls out there. If you are on broadband (DSL, cable, etc) I recommend buying a router, even if you only have one computer. It acts as a firewall. Lastly, use common sense. Programs such as Kazaa are infested with spyware. Unfortunatly, in this day and age you have to know a little background on a program you are downloading, especially if its free, simply because it costs money to create a program and that money is often retained from advertising sponsors. Hope this helps and best of luck