Direct x?

Im wanting to make an application that can (possibly) switch the display
to a lower resolution and then use the _full_ screen - I have tried
simply setting the window to be ontop of everthing else and that was
just a mess.

Basically I think I need to use direct X of some description to get the
list of available video modes and set it to one of them. Its for a full
screen control package so I dont want any dialogs to come over the top
of it. Since games work like this I was thinking direct X may have
something in it that will do the trick. I am still using delphi 3 as I
cant justify upgrading just yet.

What I am looking for is some documentation on how to use it, how to
change modes, how to draw to it etc.