Not much you can do if it is true burn in... No more 4:3 for you.. use the zoom or the fill for now on.
You will have too run the break in disc for like 1 month stright & MAYBE it will help depening on how bad it is.
Here you can get the 'break in DVD' to burn to a DVDr/rw, it is FREE (you have to unzip before burning):
http://www.avsforum.com/avs-vb/showthread.php?t=949107
which supposedly clean out an LCD screen from image sticking ?
I have an older Toshiba LCD which show permanent faint lines at the 4:3
columns. I wondered if this could be reversed by using one of those DVDs ?
Toshiba help line suggested a very colorful movie.... Is that true ?
Any help is appreciated.
Thanx

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic