D5 make main form modal

[sadsjon]

I need to make an app show a window, like a login window, but make it
system modal.

I have trawled k/b articles and tried every combination of CreateForm
and showmodal that I can in the delphi .dpr file but nothing seems to
work.

I need to make the first form process and complete before allowing any
other applications to do anything.

Is this even possible in D5?

Many thanks all,

jON