Is it possible to run plants vs zombies in 16:9 aspect ratio?
I cannot find any setting for this. The registry entries also does not help.
Go with windowed mode. There is a full screen checkbox in the game options. I have the same problem and this is what I did.
Plants vs Zombies is a 4:3 game, meaning it was designed for a normal screen. In order to fill a 16:9 screen, the game designers would have to redesign the UI for the game to accommodate this. I'm betting the reason you are asking this is that your LCD monitor is stretching the video to fill the screen (which leads to fat zombies). That is a hardware issue with your monitor. Many of the cheaper monitors don't have the ability to detect a 4:3 signal and lock the aspect ratio.
My only solution to a "fat zombie" problem is to play the game in windowed mode. Most games allow you to do that at least.
Hope this helps