>Nowadays I'm working with Axapta and see that; every form work as main form at desktop. Axapta creators decided it's more usable for end users. I think they right. I tried that at my application and faced with a problem with modal forms. Other forms can be select even form selected as "modal" when all form selected as "main form". Is there any way to fix it?

Not directly that I know of. You could cycle through the _SCREEN.Forms() collection and disable each form to prevent others from being selected. Something like

FOR lnForm=1 TO _SCREEN.FormCount
    IF _SCREEN.Forms(lnForm).Name != thisform.Name
        _SCREEN.Forms(lnForm).Enabled = .F.
    ENDIF
ENDFOR