form2 is probably modal. Until you finish form2, code will not run after line 'DO FORM form2'. So how form1 could be destroyed when its code locked?
The solutionis as follows.
Put code that runs forms into a single routine, not inside forms that are subject of running:

Do Form1
if SomeResultVariableFromPreviousRunning = .T.
Do Form2
endif
...

>I have a form that has a button that call another form. But i want release the form1 before calling the form2. Where i need to put the code?
>
>I want that the code reside inside the form1. I inclide this code inside the click event of the button in form1.
>
>THISFORM.RELEASE
>DO FORM form2
>
>But i notice that the form1 is still in memory as an Object with a .NULL. value.
>What will be happened if I open 10 forms from inside each form?
>
>Thanks,