Problem with IE6 's auto resize

hi there.

my forum's member ask me if i can solve his problem.

He use IE6 but not check "automatic resize" because he doesn't like to click enlarge to show image in full size . the problem is when width of image larger than topic width. right area of image is  missing.

how to do if i want to automatic scale down posted image to fit with topic's width or something to fix this problem ? i'm a new for php and punbb.