Within the IDE, when F12 toggles between code and form,
the forms are displayed outside the monitor borders,
and therefore not visible.
This happens after a multi monitor setup has changed,
and the forms no longer open within the available new monitor screen areas.
One way to resolve this is to use the property inspector and
set the Top/Left properties to 4 to make the forms visible.
This is however a lot of work, especially if many forms and possibly many projects are involved.
Is there a better way to reset the form locations once and for all,
so they are all visible with the new monitor setup?
There is nothing (AFAIK) in Delphi 6 IDE that would help. But assuming you are using Windows, the help is near, (tested on Windows 7):
Right-click on taskbar and select 'Cascade windows', this affects all windows in one go.
or
Alt-Tab to the window, press Alt-Space and then M (for move). Move the window with the arrow keys. This you would have to do seperately for each window.