Q. Every time I go to a website from Google, it sends me to some different website with advertising

You have a Google Redirect Virus.  It is a type of virus called a Rootkit, and can be missed by antivirus programs.

Restart your machine in Safe Mode with networking (hit F8 at start time)

Disable SpyBot TeaTimer if you have it (ignore this if you have never installed SpyBot Search and Destroy)

Download and run TDSSKiller, follow the instructions here
http://www.bleepingcomputer.com/virus-removal/remove-tdss-tdl3-alureon-rootkit-using-tdsskiller

(If you can’t download you may have to get these files on another computer and copy them to a CD or a USB memory stick)

Download these to your desktop
Malwarebytes: http://www.malwarebytes.org/mbam.php
ComboFix http://download.bleepingcomputer.com/sUBs/ComboFix.exe

before running them, change their names
Malwarebytes: mblah.scr
ComboFix: comfix.exe

Then run Malwarebytes (mblah), and clean everything it says.

Then run ComboFix (comfix), and clean everything it says. Do not click the mouse or interrupt ComboFix as it is working  If it tells you to reboot your machine during the process, do so immediately.

Information on DNSChanger and problems with Internet browsing after July 9 2012