Yea, its been changed in later versions. With yours it is set this way so that if someone posts a monster img file it want blow out the right column. That can be a good thing, but bad for us viewing on a 19" monitor while at work.
The newer versions have fixed width on img files, BUT, if you dont go and change the image file width in the ACP from 0 x 0 to something like 1024 x 1024 it will blow out the right side to accommodate their big pic. Then its a mess for us with a little monitor. Then your have a scroll bar at the bottom.
The newer versions are a bit better but more work for the admin.
The good with the bad.