Autopost back issue with listbox control

hi guys,
 
i have a very peculiar problem, i dont know if anyone of you have ever encountered this.
In my webpage, I have a listbox in which i am displaying a list of files from a directory on the server and all subdirectory names and their respective files
 
my listbox will be as follows:
 
RootFolderName
    rootfolderfile1.txt
    rootfolderfile2.txt
    abc.txt
    subfolder1
            subfolderfile1.txt
            filewithproblem.txt
    subfolder2
            filewithproblem.txt
 
The listbox looks exactly as shown above.
 
i dont have any autopostback on my listb ...