From LightWiki

It's a good idea to keep several versions of LightWave on your machine - perhaps something works better in an older version, or perhaps you have a model that can only be brought in in a specific version because of a bad plug-in in another app. In any case, LightWave is fairly forgiving in the sense that you can easily install more than one copy on your machine. The difficulty comes with config files - you don't want the 8.2 configs overwriting the 8.5 ones for instance, so you should really redirect your config files to individual locations.

The way to do this is different for PCs and Macs. You shouldn't have LightWave running in either case:

Mac OS X

1. Create a new folder inside your LightWave folder called Config
2. Go to the Programs folder inside your LightWave one and edit the file called "LightWave cmdline"
3. Double clicking on this file should open TextEdit, if not open it in that program, not Keynote
4. start typing and add "-c" then a space then quotes followed by the path to your config file directory, then end the quotes, as shown here:

-c "Macintosh HD:Applications:LightWave:LightWave 3D 9:config"

5. Copy this entire line and paste it into the the Hub cmdline and Modeler cmdline files.

Windows

1. Create a shortcut for your Layout and Modeler icons
2. Create the "Config" directory inside your LightWave directory
3. Edit the target line in the shortcut for both icons so that it has a "-c" in the target line and points to the config directory. The path should look something like this (your exact path may be different):

"C:\Program Files\Newtek\LightWave_v9.2\Programs\lightwav.exe" –c"C:\Program Files\Newtek\LightWave v9.2\Config"