When a virus is located on your computer the first thing you should do is run a full system scan on your computer to see if your internet security software is picking up any virus's.
The top virus removal security software are:-
Microsoft Security Essentials
AVG free edition
Norton Internet Security
If full system scan of your computer have failed to remove the virus from your system then you have definitely got a horrible virus on your computer and you will manually have to delete the infected files.
This example is how to remove antivirus 2011
1) Open task manager (ctrl + Alt + Delete) and "end process" to av2011.exe
2) WARNING!! Open Regedit (Start, type/select "run" and then type 'regedit"
ii) Locate HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run "av2011.exe" and delete all components of "av2011.exe"
iii) Exit out of regedit
3) Remove existing traces of av2011:
ii) Go to programs, right click on av2011 and open file located. Delete ALL files in this folder.
iii) Go to control panel select add or remove program and if you locate av2011 uninstall the program off your system
Finally Restart your machine