If you have a minimized window and want to know where it will go when you restore it, the GetWindowPlacement function will tell you. In particular, the
rcNormalPosition tells you where the window would go if it were restored (as opposed to minimized or maximized).
One perhaps-non-obvious flag is WPF_RESTORETOMAXIMIZED. This flag indicates that the window is currently minimized, but if the user selects "Restore", it will restore to its maximized instead of restored state. (This may seem strange, but you see it every day without even realizing. Take a window and maximize it. Now minimize it. Now click the taskbar button to re-open the window. Notice that it returns to its maximized state, not to its restored state. Imagine how frustrated you would be if it returned to its restored state instead. You'd have to keep re-maximizing the window.)
The GetWindowPlacement and SetWindowPlacement functions are typically used by programs that wish to save/restore window positioning information across runs.
You should also be aware that the coordinate system for window placement is not screen coordinates, but rather workspace coordinates. The consequence of getting this wrong is that your window creeps up (or to the left) over time, eventually getting itself stuck underneath the taskbar.