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If you want to get around this, rename your browser executable file names. Get rid of "avg.exe: that is located in C:\Program Files\AVG Antivirus 2011. You should also delete C:\Windows\system32\iesafemode.exe. A good antivirus such a Spyware Doctor can help rid you of this nuisance.
How does the program hijack the other browsers? It adds some registry keys in HKEY LOCAL MACHINE. Specifially there is an ImageFileExecution Options location in the registry that allows you to redirect iexplore.exe, chrome.exe, firefox.exe, and any other executable name. The fake AVG Antivirus 2011 intercepts these and all other popular web browsers. What an effort.