Hi everybody. I have this iMac: - 27" Mid 2010 - 2,93 Ghz Core i-7 - ATI Radeon HD 5750 1024 MB. Native resolution of my monitor is 2560x1440 but it's too small for me. Actually, 1920x1080 it's the perfect resolution for my eyes but it's too blurry; so I tried to use SwitcResX (4.6.6 free demo) to improve a 1920x1080 HiDPI (putting on the custom resolution panel a 3840x2160 resolution); then I saved and reboot my Mac but the 1920x1080 HiDPI resolution doesn't appear and in the SwitchRes panel is written "Not Installed". The maximum HiDPI resolution that I can have it's 1280x720 but it's too big! So i emailed Stephane Madrau and his answer was: <If "Not installed" is coming, it means that SwitchResX cannot save the resolution on the System files. That occurs when it's not able to write the file, perhaps because SIP is not disabled; or when it doesn't save the files any more, because it is not registered and it is not in trial mode any more.> Actually, before trying i disabled SIP, anyway I tried to purchase SwitchRes full version (licensed) and I tried again to custom 3840x2160...now SwitchRes said me "need reboot"... So I saved, tried to reboot but nothing.. 3840x2160 (and scaled 1920x1080 HiDPI) is not showing. Then, I tried to open SwitchRes panel but now is written " Not activeted". So...I was thinking maybe there's some problem with my GPU, my O.S. or maybe my iMac model... Can anyone help me??? I'm going mad... Thanks a lot...bye guys.