I am not sure I understand what you mean here:
can i do all this in simply displaying a second form that had gif image on it..if so,how the second form know that the processing is done in my main form and it needs to be disposed?..
If you display a second form modally from the same thread then your code that comes after the showDialog will wait until the dialog is closed before it executes ...

Do you have to do this with a "Splash Form"? You can always disable the controls on your form for the duration of the execution and then enable them again...