To install a particular hauler in the game, you first need to convert it to a MIP file using WinMip. Not sure if you can convert a PNG to a MIP. I always save my finished haulers as a BMP file, then convert it. THAT'S the easy part. Next you need to figure out the file name of the hauler you're replacing. All depends on what the track builder chose to do. Your best bet is to unpack the track using WinMip to see what they used. For instance, a red hauler might be called "truck_r". In a night track, it may be "ntruck_r". HOWEVER, if he had more than one red hauler, when you drop your new hauler in the track using that particular file name, it will replace every one of those red haulers. Builders who have used my haulers have usually given them a descriptive name like "truck99_HR". So, they only use it once and it's pretty easy to figure out... it has a number 99 somewhere on it. For older tracks, those files may be in the track's "SHARED" folder. In that case, your new hauler will show up in every track using that file. It may sound confusing, but it really isn't if you do a little research. Of course, if you can contact the builder(s) and they can tell you which hauler is which, it makes the process a WHOLE lot easier.