Well, you don't have to make them the be 1024x768... they can be 600x480 or something instead and then they will fit on anyone's monitor.
If you absolutely need to use large dialogs, then consider making everything change based on screen size. This will take a lot of work to get every dialog control to move based on the resolution, but it is possible. The best thing to do, however, is to just make smaller dialogs. Use tabs if you need more information in a single dialog box. If you really need to, then use a DLL like DCX or MDX to use smaller font sizes.
