Here is what a typical setenv.bat file contains:
@echo off
set SI_LOCATION=d:\Softimage\SOFT3D_4.0
set MI_ROOT=%SI_LOCATION%\3D\rsrc
set EFFECTS_EDITOR=notepad
set HOME=C:\users\%username%
set PARTICLE_TMPDIR=%temp%
set Path=%SI_LOCATION%\3D\bin;%SI_LOCATION%\3D\custom\bin;%SI_LOCATION%\3D\chnlDriver\bin;%SI_LOCATION%\mental_ray\bin;%SI_LOCATION%\mental_ray\MR_Shaders\Shader_Lib\lib20;%SI_LOCATION%\3D\dso;%SI_LOCATION%\3D\custom\dso;%SI_LOCATION%\3D\bin;%Path%
set SI_CHNLDRIVER=%SI_LOCATION%\3d\chnlDriver\bin
set SI_CUSTOM_ACTOR=%SI_LOCATION%\3D\custom\actor
set SI_CUSTOM_MATTER=%SI_LOCATION%\3D\custom\matter
set SI_CUSTOM_MODEL=%SI_LOCATION%\3D\custom\model
set SI_CUSTOM_MOTION=%SI_LOCATION%\3D\custom\motion
set SI_CUSTOM_TOOLS=%SI_LOCATION%\3D\custom\tools
set SI_CUSTOM_REFINE_MAX_OPT=5
set SI_CUSTOM_REFINE_PATH=%temp%
set SI_DBDIR=C:\users\%username%
set SI_FONTS=%SI_LOCATION%\3D\fonts
set SI_IMAGE_PATH=%SI_LOCATION%\3D\dso\sil
set SI_MAX_NB_POL=60000
set SI_MI_PREVIEW=%SI_LOCATION%\mental_ray\bin\mi_preview.dll
set SI_MI_TRACER2=%SI_LOCATION%\mental_ray\bin\ray2.exe
set SI_PAINT_FX=%SI_LOCATION%\3D\Pfx
set SI_MI_SPDL_DECL=
set SI_MI_SPDL_REF=
set SI_UDX_PATH=%SI_LOCATION%\3D\custom\udx
set MI_RAY2_SERVICE=mi-ray2Soft3D40
set SI_MI_SHADER_TOKEN=yes