Hello MUR,
I never heard about this problem.
Do you mean the main window of PicturesToExe, or executable presentations?
The code of PicturesToExe doesn't change brightness and technically it's impossible.
Please check what exactly happen - does your laptop sets a new brigthness of the display (see the brightness value in Display window in the Control panel), or the picture gets increased lightness (like if adjust brightness in Photoshop for images)?