>i want to do a form in a form (i can do it), another form in second form. is it possible.
>reason is my customer want to see a windows explorer like application. i think a main form, a child form left and treeview in its. another child form right and other forms in second child form.

If what you want is a similar look to Win Explorer, it uses a Treeview on the left and and ImageList control on the right. You can put anything else on the right side, like a pageframe for example instead of subforms.

HTH