Last night, using the driver for the ATI Radeon 9800 Pro for Mac, I selected "detect display" for the CRT monitor and somehow it created display mirroring for my computer when I have no second external monitor. The option to unselect mirror display disappeared from ATI driver software and there is no way for me to turn off permanently mirror display in the Display>Arrangement screen (it shows two blue screens) and the "Mirror Displays" button is still unchecked. If I check that button, it just switched to the TV version display! Unchecking the button, it switched back to my preferred monitor setting and I still have mirror displaying when I have no second monitor. See image below. Please help me to permanently turn off the mirroring display. Went to AMD website (company bought ATI) but information is not there. Thanks for any helpful, easy-to-apply information. FYI: Mac OS 10.4.11 with ATI driver 4.5.7 with a CRT monitor.