Your problem is that your system has ad-ware on it, and possibly spyware.
You need to download a program called Ad-Aware it can be found at
http://www.lavasoftusa.com/software/adaware/#free After you've done that you'll need to do a complete system scan and remove any programes it detects to be possibly spyware or possibly adware.
Adware is a programe installed on your computer usually without the your consent. And brings you unwanted advertisement usually with the opening of a web browser.
Spyware is a programe that is also usually downloaded without your acceptance and will send information about web pages you've visited, what you have on your computer and possibly information like online bank details, passwords ect to a remote computer also without your acceptance. Thefore it's best not to have any on your computer at all.