what is the difference between the windows contorl and has't windows control?

who can introduce in detail?
in my coustom system skin programme, has a container
the container has a contorl, if in the control consturct function excute createwindows();
the programme has a exe-kern 3 err?
if excute SetContainerWindowL ,the programme excute is OK?

how to salve ?
thankS!!!!!!!!