I'm running W7 pro on an iMac (2011, 21.5, budget model, SnowLeopard) using BootCamp, and using an external display (24 inch) since my eyes can't cope with the glare. The external display's native resolution is 1920x1080, same as the iMac, but the image that is outputted is smaller in size. The resolution seems to be fine, but there is a black frame of around 2 cm effectively diminishing the 24 incher to around 21.5 inch. I've tried both mirroring the image and running the external display solo - same result. The iMac's screen is normal, however. Running Mac OS X on the iMac outputs a perfect image to the external screen. Any ideas?