let’s put my problem in a simpler term —i have created a box, then deleted the top polygon so that it is an open box, when i render the picture, only the outer surfaces of the box were shown, the inner surfaces disappeared. Why is it so? and how can I fix the problem?? I need help so badly.

thanks in advance.

Your material needs to be set to 2-Sided.

Samab is correct, a two-sided material will resolve the issue.  To answer your questions, though, all surfaces in 3ds Max are single sided, they only have a surface normal pointing from one side out.  If there is not a surface normal on a particular side of an object then that surface does not render.  There are many reasons this is done including reducing rendering times.  So, in your case, the surface normals for each side of the box point outward.  When you delete the upper surface, you are now looking into the box where there are no surface normals and the inside surfaces of the box do not render.  There are a couple of methods of resolving this:

1) Use a standard material and check 2-sided.
2) Check 2-sided in the Common parameters of the Render dialog.
3) Correct the model using modifiers like Shell or Offset in Edit Poly/Mesh mode.

Stephen

Problem solved!!! :) Thanks A lot!!!!