Help! Changing Textures of objects Using Python script

I have been using Blender 2.41 for 2 months for my internship in Germany.

The situation is:

I have 2 objects named plane1 and plane2. Then 2 images (img1, img2) were attached in the objects. These images were from a folder (example C:\Images).

Are there anyone knows, how can i get images from other directories or folders (example, from C: est) to be attached to the objects ( plane1 and plane2 ) and replacing the previous images (img1 and img2) using python script? So that when the phyton script executed, the images from directory or folder C: est will be automatically attach and replace the previous images from directory C:\Images

A sample of script will be very helpful for me… Thank you very much…