Right-click on the Poser 7 desktop icon to open the contextual menu, navigate down to Properties to open that panel. Select the Compatibility tab and in the Compatibility mode area checkmark the 'Run this program in compatibility mode for: ' and select an earlier OS from the menu below it. See the image below:

Click 'Okay' and try to open Poser 7. I don't know how far back you need to go for the software to finally work. Take into consideration that certain conditions in your present OS might not be right for P7, it is a very old version. Has it ever worked before or is this a first install?