Hmm. Is your style file located in the same folder as your input file? If so, can you confirm that the display setting is set to 800x600 when you click on Options? If so, try creating two new images in your stim folder--one 800x600 and the other 1024x768. Then try to display each using your current input file. Does the 1024x768 image fill the screen? Is there blank space surrounding the 800x600 image?