I have shared the root of my C: drive on my network. 
However I can only see some folders form my other computer. For
example if I clice on documents & settings, desktop, my pictures, I
will get a message that the pictures folder is not available.
Please let me know why this is. 
I am running windows xp professional, and usning simple file sharing.
I have not restrictions on any folders.

ok there few things you have to check now

first of all you have to go to "my computer" then right click on it
and select "Properties"

select "Computer Name" and then check whether your "Workgroup Name" is
the same with the other computers. if the workgroup name is different
you cant share of see shared files.

the document and folder under c:\documents and settings\ are by itself
cant be shared.
you have to copy the folders you wanted to share to shared folders.