Print screen still works in Windows, the image being stored in the Clipboard until a new clip takes its place. You can paste the Clipboard items into an appropriate program, i.e. images to Paint and texts to Wordpad and the likes. If you need a shot of a particular window, Alt + Print Screen copies only the active window.
If you need to take a screenshot during playing AH, the best choice is Alt + S which will make a screenshot into the C:\Hitech Creations\Aces High III\scrshot folder. It takes a while for a screenshot to save so you can't make them every two seconds. 10 - 15 seconds intervals may be a reasonable expectation.
Alt + S works has been working for me in the Dx11 version as well.