Thanks for your enquiry.
TOpenDialog is a wrapper class for the Windows File Open common dialog. Unfortunately this class does not provide a way to set the screen position of the dialog. I believe the position is specified in the Windows Registry, and will change if the dialog is dragged away from its default position.
This may explain why it appears off the screen – someone has, at some point, dragged a File Open dialog to that position. Otherwise, the default position is the screen center.
I hope this helps.